diff --git a/test/api/unit/libs/slack.js b/test/api/unit/libs/slack.js
index 3252ed7e16..4b6acdf695 100644
--- a/test/api/unit/libs/slack.js
+++ b/test/api/unit/libs/slack.js
@@ -32,6 +32,7 @@ describe('slack', () => {
         },
         message: {
           id: 'chat-id',
+          username: 'author',
           user: 'Author',
           uuid: 'author-id',
           text: 'some text',
@@ -50,11 +51,11 @@ describe('slack', () => {
 
       expect(IncomingWebhook.prototype.send).to.be.calledOnce;
       expect(IncomingWebhook.prototype.send).to.be.calledWith({
-        text: 'flagger (flagger-id; language: flagger-lang) flagged a message',
+        text: 'flagger (flagger-id; language: flagger-lang) flagged a group message',
         attachments: [{
           fallback: 'Flag Message',
           color: 'danger',
-          author_name: `Author - author@example.com - author-id\n${timestamp}`,
+          author_name: `@author Author (author@example.com; author-id)\n${timestamp}`,
           title: 'Flag in Some group - (private guild)',
           title_link: undefined,
           text: 'some text',
diff --git a/test/api/v3/integration/chat/POST-chat.flag.test.js b/test/api/v3/integration/chat/POST-chat.flag.test.js
index 88b41744c8..723715c80b 100644
--- a/test/api/v3/integration/chat/POST-chat.flag.test.js
+++ b/test/api/v3/integration/chat/POST-chat.flag.test.js
@@ -63,11 +63,11 @@ describe('POST /chat/:chatId/flag', () => {
 
     /* eslint-disable camelcase */
     expect(IncomingWebhook.prototype.send).to.be.calledWith({
-      text: `${user.profile.name} (${user.id}; language: en) flagged a message`,
+      text: `${user.profile.name} (${user.id}; language: en) flagged a group message`,
       attachments: [{
         fallback: 'Flag Message',
         color: 'danger',
-        author_name: `${anotherUser.profile.name} - ${anotherUser.auth.local.email} - ${anotherUser._id}\n${timestamp}`,
+        author_name: `@${anotherUser.auth.local.username} ${anotherUser.profile.name} (${anotherUser.auth.local.email}; ${anotherUser._id})\n${timestamp}`,
         title: 'Flag in Test Guild',
         title_link: `${BASE_URL}/groups/guild/${group._id}`,
         text: TEST_MESSAGE,
@@ -98,11 +98,11 @@ describe('POST /chat/:chatId/flag', () => {
 
     /* eslint-disable camelcase */
     expect(IncomingWebhook.prototype.send).to.be.calledWith({
-      text: `${newUser.profile.name} (${newUser.id}; language: en) flagged a message`,
+      text: `${newUser.profile.name} (${newUser.id}; language: en) flagged a group message`,
       attachments: [{
         fallback: 'Flag Message',
         color: 'danger',
-        author_name: `${newUser.profile.name} - ${newUser.auth.local.email} - ${newUser._id}\n${timestamp}`,
+        author_name: `@${newUser.auth.local.username} ${newUser.profile.name} (${newUser.auth.local.email}; ${newUser._id})\n${timestamp}`,
         title: 'Flag in Test Guild',
         title_link: `${BASE_URL}/groups/guild/${group._id}`,
         text: TEST_MESSAGE,
diff --git a/test/api/v3/integration/chat/POST-chat.test.js b/test/api/v3/integration/chat/POST-chat.test.js
index bd0f158b7d..aa6b8c8806 100644
--- a/test/api/v3/integration/chat/POST-chat.test.js
+++ b/test/api/v3/integration/chat/POST-chat.test.js
@@ -257,7 +257,7 @@ describe('POST /chat', () => {
         attachments: [{
           fallback: 'Slur Message',
           color: 'danger',
-          author_name: `${user.profile.name} - ${user.auth.local.email} - ${user._id}`,
+          author_name: `@${user.auth.local.username} ${user.profile.name} (${user.auth.local.email}; ${user._id})`,
           title: 'Slur in Test Guild',
           title_link: `${BASE_URL}/groups/guild/${groupWithChat.id}`,
           text: testSlurMessage,
@@ -310,7 +310,7 @@ describe('POST /chat', () => {
         attachments: [{
           fallback: 'Slur Message',
           color: 'danger',
-          author_name: `${members[0].profile.name} - ${members[0].auth.local.email} - ${members[0]._id}`,
+          author_name: `@${members[0].auth.local.username} ${members[0].profile.name} (${members[0].auth.local.email}; ${members[0]._id})`,
           title: 'Slur in Party - (private party)',
           title_link: undefined,
           text: testSlurMessage,
diff --git a/test/api/v4/members/POST-flag_private_message.test.js b/test/api/v4/members/POST-flag_private_message.test.js
new file mode 100644
index 0000000000..dbeb9b5e18
--- /dev/null
+++ b/test/api/v4/members/POST-flag_private_message.test.js
@@ -0,0 +1,74 @@
+import {
+  generateUser,
+  translate as t,
+} from '../../../helpers/api-integration/v4';
+
+describe('POST /members/flag-private-message/:messageId', () => {
+  let userToSendMessage;
+  let messageToSend = 'Test Private Message';
+
+  beforeEach(async () => {
+    userToSendMessage = await generateUser();
+  });
+
+  it('Allows players to flag their own private message', async () => {
+    let receiver = await generateUser();
+
+    await userToSendMessage.post('/members/send-private-message', {
+      message: messageToSend,
+      toUserId: receiver._id,
+    });
+
+    let senderMessages = await userToSendMessage.get('/inbox/messages');
+
+    let sendersMessageInSendersInbox = _.find(senderMessages, (message) => {
+      return message.uuid === receiver._id && message.text === messageToSend;
+    });
+
+    expect(sendersMessageInSendersInbox).to.exist;
+    await expect(userToSendMessage.post(`/members/flag-private-message/${sendersMessageInSendersInbox.id}`)).to.eventually.be.ok;
+  });
+
+  it('Flags a private message', async () => {
+    let receiver = await generateUser();
+
+    await userToSendMessage.post('/members/send-private-message', {
+      message: messageToSend,
+      toUserId: receiver._id,
+    });
+
+    let receiversMessages = await receiver.get('/inbox/messages');
+
+    let sendersMessageInReceiversInbox = _.find(receiversMessages, (message) => {
+      return message.uuid === userToSendMessage._id && message.text === messageToSend;
+    });
+
+    expect(sendersMessageInReceiversInbox).to.exist;
+    await expect(receiver.post(`/members/flag-private-message/${sendersMessageInReceiversInbox.id}`)).to.eventually.be.ok;
+  });
+
+  it('Returns an error when user tries to flag a private message that is already flagged', async () => {
+    let receiver = await generateUser();
+
+    await userToSendMessage.post('/members/send-private-message', {
+      message: messageToSend,
+      toUserId: receiver._id,
+    });
+
+    let receiversMessages = await receiver.get('/inbox/messages');
+
+    let sendersMessageInReceiversInbox = _.find(receiversMessages, (message) => {
+      return message.uuid === userToSendMessage._id && message.text === messageToSend;
+    });
+
+    expect(sendersMessageInReceiversInbox).to.exist;
+    await expect(receiver.post(`/members/flag-private-message/${sendersMessageInReceiversInbox.id}`)).to.eventually.be.ok;
+
+    await expect(receiver.post(`/members/flag-private-message/${sendersMessageInReceiversInbox.id}`))
+      .to.eventually.be.rejected.and.eql({
+        code: 400,
+        error: 'BadRequest',
+        message: t('messageGroupChatFlagAlreadyReported'),
+      });
+  });
+});
diff --git a/website/client/components/chat/chatCard.vue b/website/client/components/chat/chatCard.vue
index 362a839f75..3a35fa1ace 100644
--- a/website/client/components/chat/chatCard.vue
+++ b/website/client/components/chat/chatCard.vue
@@ -1,8 +1,8 @@
 <template lang="pug">
 div
   .mentioned-icon(v-if='isUserMentioned')
-  .message-hidden(v-if='msg.flagCount === 1 && user.contributor.admin') Message flagged once, not hidden
-  .message-hidden(v-if='msg.flagCount > 1 && user.contributor.admin') Message hidden
+  .message-hidden(v-if='!inbox && msg.flagCount === 1 && user.contributor.admin') Message flagged once, not hidden
+  .message-hidden(v-if='!inbox && msg.flagCount > 1 && user.contributor.admin') Message hidden
   .card-body
     user-link(:userId="msg.uuid", :name="msg.user", :backer="msg.backer", :contributor="msg.contributor")
     p.time
@@ -11,25 +11,28 @@ div
       span(v-b-tooltip="", :title="msg.timestamp | date") {{ msg.timestamp | timeAgo }}&nbsp;
       span(v-if="msg.client && user.contributor.level >= 4")  ({{ msg.client }})
     .text(v-html='atHighlight(parseMarkdown(msg.text))')
+    .reported(v-if="isMessageReported && (inbox === true)")
+      span(v-once) {{ $t('reportedMessage')}}
+      br
+      span(v-once) {{ $t('canDeleteNow') }}
     hr
     .d-flex(v-if='msg.id')
       .action.d-flex.align-items-center(v-if='!inbox', @click='copyAsTodo(msg)')
         .svg-icon(v-html="icons.copy")
         div {{$t('copyAsTodo')}}
-      .action.d-flex.align-items-center(v-if='!inbox && user.flags.communityGuidelinesAccepted && msg.uuid !== "system"', @click='report(msg)')
-        .svg-icon(v-html="icons.report")
-        div {{$t('report')}}
-        // @TODO make flagging/reporting work in the inbox. NOTE: it must work even if the communityGuidelines are not accepted and it MUST work for messages that you have SENT as well as received. -- Alys
+      .action.d-flex.align-items-center(v-if='(inbox || (user.flags.communityGuidelinesAccepted && msg.uuid !== "system")) && !isMessageReported', @click='report(msg)')
+        .svg-icon(v-html="icons.report", v-once)
+        div(v-once) {{$t('report')}}
       .action.d-flex.align-items-center(v-if='msg.uuid === user._id || inbox || user.contributor.admin', @click='remove()')
-        .svg-icon(v-html="icons.delete")
-        | {{$t('delete')}}
+        .svg-icon(v-html="icons.delete", v-once)
+        div(v-once) {{$t('delete')}}
       .ml-auto.d-flex(v-b-tooltip="{title: likeTooltip(msg.likes[user._id])}", v-if='!inbox')
         .action.d-flex.align-items-center.mr-0(@click='like()', v-if='likeCount > 0', :class='{active: msg.likes[user._id]}')
           .svg-icon(v-html="icons.liked", :title='$t("liked")')
           | +{{ likeCount }}
         .action.d-flex.align-items-center.mr-0(@click='like()', v-if='likeCount === 0', :class='{active: msg.likes[user._id]}')
           .svg-icon(v-html="icons.like", :title='$t("like")')
-          span(v-if='!msg.likes[user._id]') {{ $t('like') }}
+      span(v-if='!msg.likes[user._id] && !inbox') {{ $t('like') }}
 </template>
 
 <style lang="scss">
@@ -111,6 +114,11 @@ div
       color: $purple-400;
     }
   }
+
+  .reported {
+    margin-top: 18px;
+    color: $red-50;
+  }
 </style>
 
 <script>
@@ -132,8 +140,15 @@ import reportIcon from 'assets/svg/report.svg';
 import {highlightUsers} from '../../libs/highlightUsers';
 
 export default {
-  props: ['msg', 'inbox', 'groupId'],
   components: {userLink},
+  props: {
+    msg: {},
+    inbox: {
+      type: Boolean,
+      default: false,
+    },
+    groupId: {},
+  },
   data () {
     return {
       icons: Object.freeze({
@@ -143,6 +158,7 @@ export default {
         delete: deleteIcon,
         liked: likedIcon,
       }),
+      reported: false,
     };
   },
   filters: {
@@ -191,6 +207,9 @@ export default {
       }
       return likeCount;
     },
+    isMessageReported () {
+      return this.msg.flags && this.msg.flags[this.user.id] || this.reported;
+    },
   },
   methods: {
     async like () {
@@ -216,10 +235,18 @@ export default {
     copyAsTodo (message) {
       this.$root.$emit('habitica::copy-as-todo', message);
     },
-    async report () {
+    report () {
+      this.$root.$on('habitica:report-result', data => {
+        if (data.ok) {
+          this.reported = true;
+        }
+
+        this.$root.$off('habitica:report-result');
+      });
+
       this.$root.$emit('habitica::report-chat', {
         message: this.msg,
-        groupId: this.groupId,
+        groupId: this.groupId || 'privateMessage',
       });
     },
     async remove () {
diff --git a/website/client/components/chat/chatMessages.vue b/website/client/components/chat/chatMessages.vue
index 8307720501..845e3a8bec 100644
--- a/website/client/components/chat/chatMessages.vue
+++ b/website/client/components/chat/chatMessages.vue
@@ -3,7 +3,6 @@
   .row
     .col-12
       copy-as-todo-modal(:group-type='groupType', :group-name='groupName', :group-id='groupId')
-      report-flag-modal
   div(v-for="(msg, index) in messages", v-if='chat && canViewFlag(msg)', :class='{row: inbox}')
     .d-flex(v-if='user._id !== msg.uuid', :class='{"flex-grow-1": inbox}')
       avatar.avatar-left(
@@ -105,14 +104,21 @@ import findIndex from 'lodash/findIndex';
 
 import Avatar from '../avatar';
 import copyAsTodoModal from './copyAsTodoModal';
-import reportFlagModal from './reportFlagModal';
 import chatCard from './chatCard';
 
 export default {
-  props: ['chat', 'groupType', 'groupId', 'groupName', 'inbox'],
+  props: {
+    chat: {},
+    inbox: {
+      type: Boolean,
+      default: false,
+    },
+    groupType: {},
+    groupId: {},
+    groupName: {},
+  },
   components: {
     copyAsTodoModal,
-    reportFlagModal,
     chatCard,
     Avatar,
   },
diff --git a/website/client/components/chat/reportFlagModal.vue b/website/client/components/chat/reportFlagModal.vue
index 9a96cffa2c..7dae3d3381 100644
--- a/website/client/components/chat/reportFlagModal.vue
+++ b/website/client/components/chat/reportFlagModal.vue
@@ -106,14 +106,16 @@ export default {
       this.$root.$emit('bv::hide::modal', 'report-flag');
     },
     async reportAbuse () {
-      this.notify('Thank you for reporting this violation. The moderators have been notified.');
+      this.text(this.$t(this.groupId === 'privateMessage' ? 'pmReported' : 'abuseReported'));
 
-      await this.$store.dispatch('chat:flag', {
+      let result = await this.$store.dispatch('chat:flag', {
         groupId: this.groupId,
         chatId: this.abuseObject.id,
         comment: this.reportComment,
       });
 
+      this.$root.$emit('habitica:report-result', result);
+
       this.close();
     },
     async clearFlagCount () {
diff --git a/website/client/components/header/menu.vue b/website/client/components/header/menu.vue
index 8a2ade6e13..04ae3439e6 100644
--- a/website/client/components/header/menu.vue
+++ b/website/client/components/header/menu.vue
@@ -3,6 +3,7 @@ div
   inbox-modal
   creator-intro
   profileModal
+  report-flag-modal
   send-gems-modal
   b-navbar.topbar.navbar-inverse.static-top(toggleable="lg", type="dark", :class="navbarZIndexClass")
     b-navbar-brand.brand
@@ -351,12 +352,15 @@ import profileModal from '../userMenu/profileModal';
 import sendGemsModal from 'client/components/payments/sendGemsModal';
 import userDropdown from './userDropdown';
 
+import reportFlagModal from '../chat/reportFlagModal';
+
 export default {
   components: {
     creatorIntro,
     InboxModal,
     notificationMenu,
     profileModal,
+    reportFlagModal,
     sendGemsModal,
     userDropdown,
   },
diff --git a/website/client/store/actions/chat.js b/website/client/store/actions/chat.js
index 0bb568a863..584db3bf75 100644
--- a/website/client/store/actions/chat.js
+++ b/website/client/store/actions/chat.js
@@ -48,10 +48,18 @@ export async function like (store, payload) {
 }
 
 export async function flag (store, payload) {
-  const url = `/api/v4/groups/${payload.groupId}/chat/${payload.chatId}/flag`;
+  let url = '';
+
+  if (payload.groupId === 'privateMessage') {
+    url = `/api/v4/members/flag-private-message/${payload.chatId}`;
+  } else {
+    url = `/api/v4/groups/${payload.groupId}/chat/${payload.chatId}/flag`;
+  }
+
   const response = await axios.post(url, {
     comment: payload.comment,
   });
+
   return response.data.data;
 }
 
diff --git a/website/common/errors/apiErrorMessages.js b/website/common/errors/apiErrorMessages.js
index a1550fddad..f10747b12c 100644
--- a/website/common/errors/apiErrorMessages.js
+++ b/website/common/errors/apiErrorMessages.js
@@ -8,11 +8,14 @@ module.exports = {
 
   missingTypeKeyEquip: '"key" and "type" are required parameters.',
 
+  chatIdRequired: 'req.params.chatId must contain a chatId.',
+  messageIdRequired: 'req.params.messageId must contain a message ID.',
+
   guildsOnlyPaginate: 'Only public guilds support pagination.',
   guildsPaginateBooleanString: 'req.query.paginate must be a boolean string.',
   groupIdRequired: 'req.params.groupId must contain a groupId.',
   groupRemainOrLeaveChallenges: 'req.query.keep must be either "remain-in-challenges" or "leave-challenges"',
-  managerIdRequired: 'req.body.managerId must contain a user ID.',
+  managerIdRequired: 'req.body.managerId must contain a User ID.',
   noSudoAccess: 'You don\'t have sudo access.',
 
   eventRequired: '"req.params.event" is required.',
@@ -22,6 +25,4 @@ module.exports = {
   missingCustomerId: 'Missing "req.query.customerId"',
   missingPaypalBlock: 'Missing "req.session.paypalBlock"',
   missingSubKey: 'Missing "req.query.sub"',
-
-  messageIdRequired: '\"messageId\" must be a valid UUID.",',
 };
diff --git a/website/common/locales/en/groups.json b/website/common/locales/en/groups.json
index 31b5c08887..496f1277f7 100644
--- a/website/common/locales/en/groups.json
+++ b/website/common/locales/en/groups.json
@@ -162,6 +162,7 @@
   "abuseFlagModalBody": "Are you sure you want to report this post? You should <strong>only</strong> report a post that violates the <%= firstLinkStart %>Community Guidelines<%= linkEnd %> and/or <%= secondLinkStart %>Terms of Service<%= linkEnd %>. Inappropriately reporting a post is a violation of the Community Guidelines and may give you an infraction.",
   "abuseFlagModalButton": "Report Violation",
   "abuseReported": "Thank you for reporting this violation. The moderators have been notified.",
+  "pmReported": "Thank you for reporting this message.",
   "abuseAlreadyReported": "You have already reported this message.",
   "whyReportingPost": "Why are you reporting this post?",
   "whyReportingPostPlaceholder": "Please help our moderators by letting us know why you are reporting this post for a violation, e.g., spam, swearing, religious oaths, bigotry, slurs, adult topics, violence.",
@@ -230,9 +231,9 @@
   "memberCannotRemoveYourself": "You cannot remove yourself!",
   "groupMemberNotFound": "User not found among group's members",
   "mustBeGroupMember": "Must be member of the group.",
-  "canOnlyInviteEmailUuid": "Can only invite using user IDs, emails, or usernames.",
+  "canOnlyInviteEmailUuid": "Can only invite using User IDs, emails, or usernames.",
   "inviteMissingEmail": "Missing email address in invite.",
-  "inviteMissingUuid": "Missing user id in invite",
+  "inviteMissingUuid": "Missing User ID in invite",
   "inviteMustNotBeEmpty": "Invite must not be empty.",
   "partyMustbePrivate": "Parties must be private",
   "userAlreadyInGroup": "UserID: <%= userId %>, User \"<%= username %>\" already in that group.",
diff --git a/website/common/locales/en/messages.json b/website/common/locales/en/messages.json
index 0a0e9b0c15..b1aa99d069 100644
--- a/website/common/locales/en/messages.json
+++ b/website/common/locales/en/messages.json
@@ -45,7 +45,7 @@
   "messageAuthEmailTaken": "Email already taken",
   "messageAuthNoUserFound": "No user found.",
   "messageAuthMustBeLoggedIn": "You must be logged in.",
-  "messageAuthMustIncludeTokens": "You must include a token and uid (user id) in your request",
+  "messageAuthMustIncludeTokens": "You must include a token and uid (User ID) in your request",
 
   "messageGroupAlreadyInParty": "Already in a party, try refreshing.",
   "messageGroupOnlyLeaderCanUpdate": "Only the group leader can update the group!",
@@ -71,6 +71,7 @@
   "beginningOfConversation": "This is the beginning of your conversation with <%= userName %>. Remember to be kind, respectful, and follow the Community Guidelines!",
 
   "messageDeletedUser": "Sorry, this user has deleted their account.",
-
-  "messageMissingDisplayName": "Missing display name."
+  "messageMissingDisplayName": "Missing display name.",
+  "reportedMessage": "You have reported this message to moderators.",
+  "canDeleteNow": "You can now delete the message if you wish."
 }
diff --git a/website/server/controllers/api-v3/challenges.js b/website/server/controllers/api-v3/challenges.js
index 37f9cac929..82bb301169 100644
--- a/website/server/controllers/api-v3/challenges.js
+++ b/website/server/controllers/api-v3/challenges.js
@@ -49,7 +49,7 @@ let api = {};
  * @apiSuccess {String} challenge.name Full name of challenge.
  * @apiSuccess {String} challenge.shortName A shortened name for the challenge, to be used as a tag.
  * @apiSuccess {Object} challenge.leader User details of challenge leader.
- * @apiSuccess {UUID} challenge.leader._id User id of challenge leader.
+ * @apiSuccess {UUID} challenge.leader._id User ID of challenge leader.
  * @apiSuccess {Object} challenge.leader.profile Profile information of leader.
  * @apiSuccess {Object} challenge.leader.profile.name Display Name of leader.
  * @apiSuccess {String} challenge.updatedAt Timestamp of last update.
diff --git a/website/server/controllers/api-v3/chat.js b/website/server/controllers/api-v3/chat.js
index 3c7f5468b0..84703ac0da 100644
--- a/website/server/controllers/api-v3/chat.js
+++ b/website/server/controllers/api-v3/chat.js
@@ -30,12 +30,17 @@ const FLAG_REPORT_EMAILS = nconf.get('FLAG_REPORT_EMAIL').split(',').map((email)
 
 /**
  * @apiDefine GroupIdRequired
- * @apiError (404) {badRequest} groupIdRequired A group ID is required
+ * @apiError (400) {badRequest} groupIdRequired A group ID is required
  */
 
 /**
  * @apiDefine ChatIdRequired
- * @apiError (404) {badRequest} chatIdRequired A chat ID is required
+ * @apiError (400) {badRequest} chatIdRequired A chat ID is required
+ */
+
+/**
+ * @apiDefine MessageIdRequired
+ * @apiError (400) {badRequest} messageIdRequired A message ID is required
  */
 
 let api = {};
@@ -246,7 +251,7 @@ api.likeChat = {
     let groupId = req.params.groupId;
 
     req.checkParams('groupId', apiError('groupIdRequired')).notEmpty();
-    req.checkParams('chatId', res.t('chatIdRequired')).notEmpty();
+    req.checkParams('chatId', apiError('chatIdRequired')).notEmpty();
 
     let validationErrors = req.validationErrors();
     if (validationErrors) throw validationErrors;
@@ -285,7 +290,7 @@ api.likeChat = {
  * @apiSuccess {Object} data.likes The likes of the message
  * @apiSuccess {Object} data.flags The flags of the message
  * @apiSuccess {Number} data.flagCount The number of flags the message has
- * @apiSuccess {UUID} data.uuid The user id of the author of the message
+ * @apiSuccess {UUID} data.uuid The User ID of the author of the message
  * @apiSuccess {String} data.user The username of the author of the message
  *
  * @apiUse GroupNotFound
@@ -334,7 +339,7 @@ api.clearChatFlags = {
     let chatId = req.params.chatId;
 
     req.checkParams('groupId', apiError('groupIdRequired')).notEmpty();
-    req.checkParams('chatId', res.t('chatIdRequired')).notEmpty();
+    req.checkParams('chatId', apiError('chatIdRequired')).notEmpty();
 
     let validationErrors = req.validationErrors();
     if (validationErrors) throw validationErrors;
@@ -470,7 +475,7 @@ api.deleteChat = {
     let chatId = req.params.chatId;
 
     req.checkParams('groupId', apiError('groupIdRequired')).notEmpty();
-    req.checkParams('chatId', res.t('chatIdRequired')).notEmpty();
+    req.checkParams('chatId', apiError('chatIdRequired')).notEmpty();
 
     let validationErrors = req.validationErrors();
     if (validationErrors) throw validationErrors;
diff --git a/website/server/controllers/api-v3/groups.js b/website/server/controllers/api-v3/groups.js
index 166f82e430..9eef5108e9 100644
--- a/website/server/controllers/api-v3/groups.js
+++ b/website/server/controllers/api-v3/groups.js
@@ -941,11 +941,11 @@ api.removeGroupMember = {
  *     {"name": "User2", "email": "user-2@example.com"}
  *   ]
  * }
- * @apiParamExample {json} User Ids
+ * @apiParamExample {json} User IDs
  *   {
  *     "uuids": ["user-id-of-existing-user", "user-id-of-another-existing-user"]
  *   }
- * @apiParamExample {json} User Ids and Emails
+ * @apiParamExample {json} User IDs and Emails
  * {
  *   "emails": [
  *       {"email": "user-1@example.com"},
@@ -955,7 +955,7 @@ api.removeGroupMember = {
  * }
  *
  * @apiSuccess {Array} data The invites
- * @apiSuccess {Object} data[0] If the invitation was a user id, you'll receive back an object. You'll receive one Object for each succesful user id invite.
+ * @apiSuccess {Object} data[0] If the invitation was a User ID, you'll receive back an object. You'll receive one Object for each succesful User ID invite.
  * @apiSuccess {String} data[1] If the invitation was an email, you'll receive back the email. You'll receive one String for each successful email invite.
  *
  * @apiSuccessExample {json} Successful Response with Emails
@@ -966,13 +966,13 @@ api.removeGroupMember = {
  *   ]
  * }
  *
- * @apiSuccessExample {json} Successful Response with User Id
+ * @apiSuccessExample {json} Successful Response with User ID
  * {
  *   "data": [
  *     { id: 'the-id-of-the-invited-user', name: 'The group name', inviter: 'your-user-id' }
  *   ]
  * }
- * @apiSuccessExample {json} Successful Response with User Ids and Emails
+ * @apiSuccessExample {json} Successful Response with User IDs and Emails
  * {
  *   "data": [
  *     "user-1@example.com",
@@ -987,9 +987,9 @@ api.removeGroupMember = {
  * param `Array`.
  * @apiError (400) {BadRequest} UuidOrEmailOnly The `emails` and `uuids` params were both missing and/or a
  * key other than `emails` or `uuids` was provided in the body param.
- * @apiError (400) {BadRequest} CannotInviteSelf User id or email of invitee matches that of the inviter.
+ * @apiError (400) {BadRequest} CannotInviteSelf User ID or email of invitee matches that of the inviter.
  * @apiError (400) {BadRequest} MustBeArray The `uuids` or `emails` body param was not an array.
- * @apiError (400) {BadRequest} TooManyInvites A max of 100 invites (combined emails and user ids) can
+ * @apiError (400) {BadRequest} TooManyInvites A max of 100 invites (combined emails and User IDs) can
  * be sent out at a time.
  * @apiError (400) {BadRequest} ExceedsMembersLimit A max of 30 members can join a party.
  *
diff --git a/website/server/controllers/api-v3/hall.js b/website/server/controllers/api-v3/hall.js
index e42adb80c5..d3715bfda6 100644
--- a/website/server/controllers/api-v3/hall.js
+++ b/website/server/controllers/api-v3/hall.js
@@ -197,7 +197,7 @@ const gemsPerTier = {1: 3, 2: 3, 3: 3, 4: 4, 5: 4, 6: 4, 7: 4, 8: 0, 9: 0};
 
 /**
  * @api {put} /api/v3/hall/heroes/:heroId Update any user ("hero")
- * @apiParam (Path) {UUID} heroId user ID
+ * @apiParam (Path) {UUID} heroId User ID
  * @apiName UpdateHero
  * @apiGroup Hall
  * @apiPermission Admin
diff --git a/website/server/controllers/api-v4/members.js b/website/server/controllers/api-v4/members.js
new file mode 100644
index 0000000000..57a1b39ddd
--- /dev/null
+++ b/website/server/controllers/api-v4/members.js
@@ -0,0 +1,43 @@
+import { authWithHeaders } from '../../middlewares/auth';
+import { chatReporterFactory } from '../../libs/chatReporting/chatReporterFactory';
+
+let api = {};
+
+/**
+ * @api {post} /api/v4/members/flag-private-message/:messageId Flag a private message
+ * @apiDescription An email and slack message are sent to the moderators about every flagged message.
+ * @apiName FlagPrivateMessage
+ * @apiGroup Member
+ *
+ * @apiParam (Path) {UUID} messageId The private message id
+ *
+ * @apiSuccess {Object} data The flagged private message
+ * @apiSuccess {UUID} data.id The id of the message
+ * @apiSuccess {String} data.text The text of the message
+ * @apiSuccess {Number} data.timestamp The timestamp of the message in milliseconds
+ * @apiSuccess {Object} data.likes The likes of the message (always an empty object)
+ * @apiSuccess {Object} data.flags The flags of the message
+ * @apiSuccess {Number} data.flagCount The number of flags the message has
+ * @apiSuccess {UUID} data.uuid The User ID of the author of the message, or of the recipient if `sent` is true
+ * @apiSuccess {String} data.user The Display Name of the author of the message, or of the recipient if `sent` is true
+ * @apiSuccess {String} data.username The Username of the author of the message, or of the recipient if `sent` is true
+ *
+ * @apiUse MessageNotFound
+ * @apiUse MessageIdRequired
+ * @apiError (400) {BadRequest} messageGroupChatFlagAlreadyReported You have already reported this message
+ */
+api.flagPrivateMessage = {
+  method: 'POST',
+  url: '/members/flag-private-message/:messageId',
+  middlewares: [authWithHeaders()],
+  async handler (req, res) {
+    const chatReporter = chatReporterFactory('Inbox', req, res);
+    const message = await chatReporter.flag();
+    res.respond(200, {
+      ok: true,
+      message,
+    });
+  },
+};
+
+module.exports = api;
diff --git a/website/server/libs/chatReporting/chatReporter.js b/website/server/libs/chatReporting/chatReporter.js
index 148dbd4696..d55a95c353 100644
--- a/website/server/libs/chatReporting/chatReporter.js
+++ b/website/server/libs/chatReporting/chatReporter.js
@@ -1,6 +1,4 @@
-import {
-} from '../errors';
-import { getUserInfo } from '../email';
+import { getGroupUrl, getUserInfo } from '../email';
 import { getAuthorEmailFromMessage } from '../chat';
 
 export default class ChatReporter {
@@ -11,25 +9,51 @@ export default class ChatReporter {
 
   async validate () {}
 
-  async notify (group, message) {
-    const reporterEmailContent = getUserInfo(this.user, ['email']).email;
-    this.authorEmail = await getAuthorEmailFromMessage(message);
-    this.emailVariables = [
+  async getMessageVariables (group, message) {
+    const reporterEmail = getUserInfo(this.user, ['email']).email;
+
+    const authorVariables = await this.getAuthorVariables(message);
+    const groupUrl = getGroupUrl(group);
+
+    return [
       {name: 'MESSAGE_TIME', content: (new Date(message.timestamp)).toString()},
       {name: 'MESSAGE_TEXT', content: message.text},
 
-      {name: 'REPORTER_USERNAME', content: this.user.profile.name},
+      {name: 'REPORTER_DISPLAY_NAME', content: this.user.profile.name},
+      {name: 'REPORTER_USERNAME', content: this.user.auth.local.username},
       {name: 'REPORTER_UUID', content: this.user._id},
-      {name: 'REPORTER_EMAIL', content: reporterEmailContent},
+      {name: 'REPORTER_EMAIL', content: reporterEmail},
       {name: 'REPORTER_MODAL_URL', content: `/static/front/#?memberId=${this.user._id}`},
 
-      {name: 'AUTHOR_USERNAME', content: message.user},
-      {name: 'AUTHOR_UUID', content: message.uuid},
-      {name: 'AUTHOR_EMAIL', content: this.authorEmail},
-      {name: 'AUTHOR_MODAL_URL', content: `/static/front/#?memberId=${message.uuid}`},
+      ...authorVariables,
+
+      {name: 'GROUP_NAME', content: group.name},
+      {name: 'GROUP_TYPE', content: group.type},
+      {name: 'GROUP_ID', content: group._id},
+      {name: 'GROUP_URL', content: groupUrl || 'N/A'},
     ];
   }
 
+  createGenericAuthorVariables (prefix, {user, username, uuid, email}) {
+    return [
+      {name: `${prefix}_DISPLAY_NAME`, content: user},
+      {name: `${prefix}_USERNAME`, content: username},
+      {name: `${prefix}_UUID`, content: uuid},
+      {name: `${prefix}_EMAIL`, content: email},
+      {name: `${prefix}_MODAL_URL`, content: `/static/front/#?memberId=${uuid}`},
+    ];
+  }
+
+  async getAuthorVariables (message) {
+    this.authorEmail = await getAuthorEmailFromMessage(message);
+    return this.createGenericAuthorVariables('AUTHOR', {
+      user: message.user,
+      username: message.username,
+      uuid: message.uuid,
+      email: this.authorEmail,
+    });
+  }
+
   async flag () {
     throw new Error('Flag must be implemented');
   }
diff --git a/website/server/libs/chatReporting/chatReporterFactory.js b/website/server/libs/chatReporting/chatReporterFactory.js
index cd97da6793..50ac7e9e89 100644
--- a/website/server/libs/chatReporting/chatReporterFactory.js
+++ b/website/server/libs/chatReporting/chatReporterFactory.js
@@ -1,11 +1,10 @@
 import GroupChatReporter from './groupChatReporter';
-// import InboxChatReporter from './inboxChatReporter';
+import InboxChatReporter from './inboxChatReporter';
 
 export function chatReporterFactory (type, req, res) {
   if (type === 'Group') {
     return new GroupChatReporter(req, res);
+  } else if (type === 'Inbox') {
+    return new InboxChatReporter(req, res);
   }
-  // else if (type === 'Inbox') {
-  //   return new InboxChatReporter(req, res);
-  // }
 }
diff --git a/website/server/libs/chatReporting/groupChatReporter.js b/website/server/libs/chatReporting/groupChatReporter.js
index ff625bfb8a..b41f142579 100644
--- a/website/server/libs/chatReporting/groupChatReporter.js
+++ b/website/server/libs/chatReporting/groupChatReporter.js
@@ -6,7 +6,7 @@ import {
   BadRequest,
   NotFound,
 } from '../errors';
-import { getGroupUrl, sendTxn } from '../email';
+import { sendTxn } from '../email';
 import slack from '../slack';
 import { model as Group } from '../../models/group';
 import { chatModel as Chat } from '../../models/message';
@@ -28,7 +28,7 @@ export default class GroupChatReporter extends ChatReporter {
 
   async validate () {
     this.req.checkParams('groupId', apiError('groupIdRequired')).notEmpty();
-    this.req.checkParams('chatId', this.res.t('chatIdRequired')).notEmpty();
+    this.req.checkParams('chatId', apiError('chatIdRequired')).notEmpty();
 
     let validationErrors = this.req.validationErrors();
     if (validationErrors) throw validationErrors;
@@ -50,16 +50,12 @@ export default class GroupChatReporter extends ChatReporter {
   }
 
   async notify (group, message, userComment, automatedComment = '') {
-    await super.notify(group, message);
-
-    const groupUrl = getGroupUrl(group);
-    sendTxn(FLAG_REPORT_EMAILS, 'flag-report-to-mods-with-comments', this.emailVariables.concat([
-      {name: 'GROUP_NAME', content: group.name},
-      {name: 'GROUP_TYPE', content: group.type},
-      {name: 'GROUP_ID', content: group._id},
-      {name: 'GROUP_URL', content: groupUrl},
+    let emailVariables = await this.getMessageVariables(group, message);
+    emailVariables = emailVariables.concat([
       {name: 'REPORTER_COMMENT', content: userComment || ''},
-    ]));
+    ]);
+
+    sendTxn(FLAG_REPORT_EMAILS, 'flag-report-to-mods-with-comments', emailVariables);
 
     slack.sendFlagNotification({
       authorEmail: this.authorEmail,
diff --git a/website/server/libs/chatReporting/inboxChatReporter.js b/website/server/libs/chatReporting/inboxChatReporter.js
new file mode 100644
index 0000000000..207b570fd3
--- /dev/null
+++ b/website/server/libs/chatReporting/inboxChatReporter.js
@@ -0,0 +1,129 @@
+import nconf from 'nconf';
+import { model as User } from '../../models/user';
+
+import ChatReporter from './chatReporter';
+import {
+  BadRequest,
+} from '../errors';
+import { getUserInfo, sendTxn} from '../email';
+import slack from '../slack';
+import apiError from '../apiError';
+
+import * as inboxLib from '../inbox';
+import {getAuthorEmailFromMessage} from '../chat';
+
+const FLAG_REPORT_EMAILS = nconf.get('FLAG_REPORT_EMAIL').split(',').map((email) => {
+  return { email, canSend: true };
+});
+
+export default class InboxChatReporter extends ChatReporter {
+  constructor (req, res) {
+    super(req, res);
+
+    this.user = res.locals.user;
+    this.inboxUser = res.locals.user;
+  }
+
+  async validate () {
+    this.req.checkParams('messageId', apiError('messageIdRequired')).notEmpty();
+
+    let validationErrors = this.req.validationErrors();
+    if (validationErrors) throw validationErrors;
+
+    if (this.user.contributor.admin && this.req.query.userId) {
+      this.inboxUser = await User.findOne({_id: this.req.query.userId});
+    }
+
+    const message = await inboxLib.getUserInboxMessage(this.inboxUser, this.req.params.messageId);
+    if (!message) throw new BadRequest(this.res.t('messageGroupChatNotFound'));
+
+    const userComment = this.req.body.comment;
+
+    return {message, userComment};
+  }
+
+  async notify (message, userComment) {
+    const group = {
+      type: 'private messages',
+      name: 'N/A',
+      _id: 'N/A',
+    };
+
+    let emailVariables = await this.getMessageVariables(group, message);
+    emailVariables = emailVariables.concat([
+      {name: 'REPORTER_COMMENT', content: userComment || ''},
+    ]);
+
+    sendTxn(FLAG_REPORT_EMAILS, 'flag-report-to-mods-with-comments', emailVariables);
+
+    slack.sendInboxFlagNotification({
+      authorEmail: this.authorEmail,
+      flagger: this.user,
+      message,
+      userComment,
+    });
+  }
+
+  async getAuthorVariables (message) {
+    const messageUser = {
+      user: message.user,
+      username: message.username,
+      uuid: message.uuid,
+      email: await getAuthorEmailFromMessage(message),
+    };
+
+    const reporter = {
+      user: this.user.profile.name,
+      username: this.user.auth.local.username,
+      uuid: this.user._id,
+      email: getUserInfo(this.user, ['email']).email,
+    };
+
+    // if message.sent, the reporter is the author of this message
+    const sendingUser = message.sent ? reporter : messageUser;
+    const recipient = message.sent ? messageUser : reporter;
+
+    this.authorEmail = sendingUser.email;
+
+    return [
+      ...this.createGenericAuthorVariables('AUTHOR', sendingUser),
+      ...this.createGenericAuthorVariables('RECIPIENT', recipient),
+    ];
+  }
+
+  updateMessageAndSave (message, ...changedFields) {
+    for (const changedField of changedFields) {
+      message.markModified(changedField);
+    }
+
+    return message.save();
+  }
+
+  flagInboxMessage (message) {
+    // Log user ids that have flagged the message
+    if (!message.flags) message.flags = {};
+    // TODO fix error type
+    if (message.flags[this.user._id] && !this.user.contributor.admin) {
+      throw new BadRequest(this.res.t('messageGroupChatFlagAlreadyReported'));
+    }
+
+    message.flags[this.user._id] = true;
+    message.flagCount = 1;
+
+    return this.updateMessageAndSave(message, 'flags', 'flagCount');
+  }
+
+  async markMessageAsReported (message) {
+    message.reported = true;
+
+    return this.updateMessageAndSave(message, 'reported');
+  }
+
+  async flag () {
+    let {message, userComment} = await this.validate();
+    await this.flagInboxMessage(message);
+    await this.notify(message, userComment);
+    await this.markMessageAsReported(message);
+    return message;
+  }
+}
diff --git a/website/server/libs/inbox/index.js b/website/server/libs/inbox/index.js
index cbdda9d8e2..26524ecac0 100644
--- a/website/server/libs/inbox/index.js
+++ b/website/server/libs/inbox/index.js
@@ -16,6 +16,10 @@ export async function getUserInbox (user, asArray = true) {
   }
 }
 
+export async function getUserInboxMessage (user, messageId) {
+  return Inbox.findOne({ownerId: user._id, _id: messageId}).exec();
+}
+
 export async function deleteMessage (user, messageId) {
   const message = await Inbox.findOne({_id: messageId, ownerId: user._id }).exec();
   if (!message) return false;
diff --git a/website/server/libs/setupPassport.js b/website/server/libs/setupPassport.js
index 9f17200fd1..215c91daa5 100644
--- a/website/server/libs/setupPassport.js
+++ b/website/server/libs/setupPassport.js
@@ -6,7 +6,7 @@ import { Strategy as GoogleStrategy } from 'passport-google-oauth20';
 // Passport session setup.
 //   To support persistent login sessions, Passport needs to be able to
 //   serialize users into and deserialize users out of the session.  Typically,
-//   this will be as simple as storing the user ID when serializing, and finding
+//   this will be as simple as storing the User ID when serializing, and finding
 //   the user by ID when deserializing.  However, since this example does not
 //   have a database of user records, the complete Facebook profile is serialized
 //   and deserialized.
diff --git a/website/server/libs/slack.js b/website/server/libs/slack.js
index b0b5bb8898..0adaf24894 100644
--- a/website/server/libs/slack.js
+++ b/website/server/libs/slack.js
@@ -9,6 +9,10 @@ const SLACK_FLAGGING_URL = nconf.get('SLACK_FLAGGING_URL');
 const SLACK_FLAGGING_FOOTER_LINK = nconf.get('SLACK_FLAGGING_FOOTER_LINK');
 const SLACK_SUBSCRIPTIONS_URL = nconf.get('SLACK_SUBSCRIPTIONS_URL');
 const BASE_URL = nconf.get('BASE_URL');
+const IS_PRODUCTION = nconf.get('IS_PROD');
+
+const SKIP_FLAG_METHODS = IS_PRODUCTION && !SLACK_FLAGGING_URL;
+const SKIP_SUB_METHOD = IS_PRODUCTION && !SLACK_SUBSCRIPTIONS_URL;
 
 let flagSlack;
 let subscriptionSlack;
@@ -18,6 +22,26 @@ try {
   subscriptionSlack = new IncomingWebhook(SLACK_SUBSCRIPTIONS_URL);
 } catch (err) {
   logger.error(err);
+
+  if (!IS_PRODUCTION) {
+    flagSlack = subscriptionSlack = {
+      send (data) {
+        logger.info('Data sent to slack', data);
+      },
+    };
+  }
+}
+
+/**
+ *
+ * @param formatObj.name userName
+ * @param formatObj.displayName displayName
+ * @param formatObj.email email
+ * @param formatObj.uuid uuid
+ * @returns {string}
+ */
+function formatUser (formatObj) {
+  return `@${formatObj.name} ${formatObj.displayName} (${formatObj.email}; ${formatObj.uuid})`;
 }
 
 function sendFlagNotification ({
@@ -28,13 +52,13 @@ function sendFlagNotification ({
   userComment,
   automatedComment,
 }) {
-  if (!SLACK_FLAGGING_URL) {
+  if (SKIP_FLAG_METHODS) {
     return;
   }
   let titleLink;
   let authorName;
   let title = `Flag in ${group.name}`;
-  let text = `${flagger.profile.name} (${flagger.id}; language: ${flagger.preferences.language}) flagged a message`;
+  let text = `${flagger.profile.name} (${flagger.id}; language: ${flagger.preferences.language}) flagged a group message`;
   let footer = `<${SLACK_FLAGGING_FOOTER_LINK}?groupId=${group.id}&chatId=${message.id}|Flag this message.>`;
 
   if (userComment) {
@@ -55,7 +79,12 @@ function sendFlagNotification ({
   if (!message.user && message.uuid === 'system') {
     authorName = 'System Message';
   } else {
-    authorName = `${message.user} - ${authorEmail} - ${message.uuid}`;
+    authorName = formatUser({
+      name: message.username,
+      displayName: message.user,
+      email: authorEmail,
+      uuid: message.uuid,
+    });
   }
 
   const timestamp = `${moment(message.timestamp).utc().format('YYYY-MM-DD HH:mm')} UTC`;
@@ -77,6 +106,69 @@ function sendFlagNotification ({
   });
 }
 
+function sendInboxFlagNotification ({
+  authorEmail,
+  flagger,
+  message,
+  userComment,
+}) {
+  if (SKIP_FLAG_METHODS) {
+    return;
+  }
+  let titleLink = '';
+  let authorName;
+  let title = `Flag in ${flagger.profile.name}'s Inbox`;
+  let text = `${flagger.profile.name} (${flagger.id}; language: ${flagger.preferences.language}) flagged a PM`;
+  let footer = '';
+
+  if (userComment) {
+    text += ` and commented: ${userComment}`;
+  }
+
+  let messageText = message.text;
+  let sender = '';
+  let recipient = '';
+
+  const flaggerFormat = formatUser({
+    displayName: flagger.profile.name,
+    name: flagger.auth.local.username,
+    email: flagger.auth.local.email,
+    uuid: flagger._id,
+  });
+  const messageUserFormat = formatUser({
+    displayName: message.user,
+    name: message.username,
+    email: authorEmail,
+    uuid: message.uuid,
+  });
+
+  if (message.sent) {
+    sender = flaggerFormat;
+    recipient = messageUserFormat;
+  } else {
+    sender = messageUserFormat;
+    recipient = flaggerFormat;
+  }
+
+  authorName = `${sender} wrote this message to ${recipient}.`;
+
+  flagSlack.send({
+    text,
+    attachments: [{
+      fallback: 'Flag Message',
+      color: 'danger',
+      author_name: authorName,
+      title,
+      title_link: titleLink,
+      text: messageText,
+      footer,
+      mrkdwn_in: [
+        'text',
+      ],
+    }],
+  });
+}
+
 function sendSubscriptionNotification ({
   buyer,
   recipient,
@@ -84,7 +176,7 @@ function sendSubscriptionNotification ({
   months,
   groupId,
 }) {
-  if (!SLACK_SUBSCRIPTIONS_URL) {
+  if (SKIP_SUB_METHOD) {
     return;
   }
   let text;
@@ -108,7 +200,7 @@ function sendSlurNotification ({
   group,
   message,
 }) {
-  if (!SLACK_FLAGGING_URL) {
+  if (SKIP_FLAG_METHODS) {
     return;
   }
   let titleLink;
@@ -124,7 +216,12 @@ function sendSlurNotification ({
     title += ` - (${group.privacy} ${group.type})`;
   }
 
-  authorName = `${author.profile.name} - ${authorEmail} - ${author.id}`;
+  authorName = formatUser({
+    name: author.auth.local.username,
+    displayName: author.profile.name,
+    email: authorEmail,
+    uuid: author.id,
+  });
 
   flagSlack.send({
     text,
@@ -143,5 +240,9 @@ function sendSlurNotification ({
 }
 
 module.exports = {
-  sendFlagNotification, sendSubscriptionNotification, sendSlurNotification,
+  sendFlagNotification,
+  sendInboxFlagNotification,
+  sendSubscriptionNotification,
+  sendSlurNotification,
+  formatUser,
 };
diff --git a/website/server/models/group.js b/website/server/models/group.js
index cea35d21ad..e8bf77e39a 100644
--- a/website/server/models/group.js
+++ b/website/server/models/group.js
@@ -408,7 +408,7 @@ function getInviteCount (uuids, emails) {
 /**
  * Checks invitation uuids and emails for possible errors.
  *
- * @param  uuids  An array of user ids
+ * @param  uuids  An array of User IDs
  * @param  emails  An array of emails
  * @param  res  Express res object for use with translations
  * @throws BadRequest An error describing the issue with the invitations