diff --git a/src/views/email.html b/src/views/email.html
index 3d6f2ed13..3c66638f9 100644
--- a/src/views/email.html
+++ b/src/views/email.html
@@ -107,12 +107,12 @@
               <div class="input-group-addon">@{{ selectedDomain.domain }}</div>
             </div>
           </div>
-          <input class="hide" type="submit" ng-disabled="mailboxedit_form.$invalid || mailboxes.edit.busy"/>
+          <input class="hide" type="submit" ng-disabled="mailboxedit_form.$invalid || mailboxes.edit.busy || !mailboxes.edit.owner"/>
         </form>
       </div>
       <div class="modal-footer">
         <button type="button" class="btn btn-default" data-dismiss="modal">Cancel</button>
-        <button type="button" class="btn btn-success" ng-click="mailboxes.edit.submit()" ng-disabled="mailboxedit_form.$invalid || mailboxes.edit.busy"><i class="fa fa-circle-notch fa-spin" ng-show="mailboxes.edit.busy"></i> Save</button>
+        <button type="button" class="btn btn-success" ng-click="mailboxes.edit.submit()" ng-disabled="mailboxedit_form.$invalid || mailboxes.edit.busy || !mailboxes.edit.owner"><i class="fa fa-circle-notch fa-spin" ng-show="mailboxes.edit.busy"></i> Save</button>
       </div>
     </div>
   </div>
diff --git a/src/views/email.js b/src/views/email.js
index 120d2f7d5..0b453113c 100644
--- a/src/views/email.js
+++ b/src/views/email.js
@@ -286,7 +286,7 @@ angular.module('Application').controller('EmailController', ['$scope', '$locatio
 
             show: function (mailbox) {
                 $scope.mailboxes.edit.name = mailbox.name;
-                $scope.mailboxes.edit.owner = mailbox.owner;
+                $scope.mailboxes.edit.owner = mailbox.owner; // this can be null if mailbox had no owner
                 $scope.mailboxes.edit.aliases = mailbox.aliases;
 
                 $('#mailboxEditModal').modal('show');
@@ -295,6 +295,7 @@ angular.module('Application').controller('EmailController', ['$scope', '$locatio
             submit: function () {
                 $scope.mailboxes.edit.busy = true;
 
+                // $scope.mailboxes.edit.owner is expected to be validated by the UI
                 Client.updateMailbox($scope.selectedDomain.domain, $scope.mailboxes.edit.name, $scope.mailboxes.edit.owner.id, function (error) {
                     if (error) {
                         $scope.mailboxes.edit.error = error;
@@ -364,8 +365,8 @@ angular.module('Application').controller('EmailController', ['$scope', '$locatio
 
                     $scope.mailboxes.mailboxes = mailboxes.map(function (m) {
                         m.aliases = aliases.filter(function (a) { return a.aliasTarget === m.name; }).map(function (a) { return a.name; }).join(',');
-                        m.owner = $scope.users.find(function (u) { return u.id === m.ownerId; });
-                        m.ownerDisplayName = m.owner.display; // this meta property is set when we get the user list
+                        m.owner = $scope.users.find(function (u) { return u.id === m.ownerId; }); // owner may not exist
+                        m.ownerDisplayName = m.owner ? m.owner.display : ''; // this meta property is set when we get the user list
 
                         return m;
                     });