Log when and why an email was not sent in email_logs

app/assets/javascripts/admin/models/email_log.js

@@ -20,7 +20,7 @@ Discourse.EmailLog.reopenClass({
 
   findAll: function(filter) {
     var result = Em.A();
-    Discourse.ajax("/admin/email/logs.json", {
+    Discourse.ajax("/admin/email/" + (filter === 'skipped' ? 'skipped' : 'logs') + ".json", {
       data: { filter: filter }
     }).then(function(logs) {
       _.each(logs,function(log) {

app/assets/javascripts/admin/routes/admin_email_skipped_route.js

@@ -0,0 +1,17 @@
+/**
+  Handles routes related to viewing email logs of emails that were NOT sent.
+
+  @class AdminEmailSkippedRoute
+  @extends Discourse.Route
+  @namespace Discourse
+  @module Discourse
+**/
+Discourse.AdminEmailSkippedRoute = Discourse.Route.extend({
+  model: function() {
+    return Discourse.EmailLog.findAll('skipped');
+  },
+
+  renderTemplate: function() {
+    this.render('admin/templates/email_skipped', {into: 'adminEmail'});
+  }
+});

app/assets/javascripts/admin/routes/admin_routes.js

@@ -17,6 +17,7 @@ Discourse.Route.buildRoutes(function() {
 
     this.resource('adminEmail', { path: '/email'}, function() {
       this.route('logs');
+      this.route('skipped');
       this.route('previewDigest', { path: '/preview-digest' });
     });
 

app/assets/javascripts/admin/templates/email.js.handlebars

@@ -3,6 +3,7 @@
     <ul class="nav nav-pills">
       <li>{{#link-to 'adminEmail.index'}}{{i18n admin.email.settings}}{{/link-to}}</li>
       <li>{{#link-to 'adminEmail.logs'}}{{i18n admin.email.logs}}{{/link-to}}</li>
+      <li>{{#link-to 'adminEmail.skipped'}}{{i18n admin.email.skipped}}{{/link-to}}</li>
       <li>{{#link-to 'adminEmail.previewDigest'}}{{i18n admin.email.preview_digest}}{{/link-to}}</li>
     </ul>
   </div>

app/assets/javascripts/admin/templates/email_skipped.js.handlebars

@@ -0,0 +1,33 @@
+<table class='table'>
+  <thead>
+    <tr>
+      <th>{{i18n admin.email.sent_at}}</th>
+      <th>{{i18n admin.email.user}}</th>
+      <th>{{i18n admin.email.to_address}}</th>
+      <th>{{i18n admin.email.email_type}}</th>
+      <th>{{i18n admin.email.skip_reason}}</th>
+    </tr>
+  </thead>
+
+  {{#if model.length}}
+    {{#groupedEach model}}
+      <tr>
+        <td>{{unboundDate created_at}}</td>
+        <td>
+          {{#if user}}
+            {{#link-to 'adminUser' user}}{{avatar user imageSize="tiny"}}{{/link-to}}
+            {{#link-to 'adminUser' user}}{{user.username}}{{/link-to}}
+          {{else}}
+            &mdash;
+          {{/if}}
+        </td>
+        <td><a href='mailto:{{unbound to_address}}'>{{to_address}}</a></td>
+        <td>{{email_type}}</td>
+        <td>
+          {{skipped_reason}}
+        </td>
+      </tr>
+    {{/groupedEach}}
+  {{/if}}
+
+</table>