diff --git a/assets/js/src/newsletters/listings/mixins.jsx b/assets/js/src/newsletters/listings/mixins.jsx
index 0b6204a6b9..f3ecfde41a 100644
--- a/assets/js/src/newsletters/listings/mixins.jsx
+++ b/assets/js/src/newsletters/listings/mixins.jsx
@@ -8,7 +8,9 @@ const _QueueMixin = {
     MailPoet.Ajax.post({
       endpoint: 'sendingQueue',
       action: 'pause',
-      data: newsletter.id
+      data: {
+        id: newsletter.id
+      }
     }).done(function() {
       jQuery('#resume_'+newsletter.id).show();
       jQuery('#pause_'+newsletter.id).hide();
@@ -18,7 +20,9 @@ const _QueueMixin = {
     MailPoet.Ajax.post({
       endpoint: 'sendingQueue',
       action: 'resume',
-      data: newsletter.id
+      data: {
+        id: newsletter.id
+      }
     }).done(function() {
       jQuery('#pause_'+newsletter.id).show();
       jQuery('#resume_'+newsletter.id).hide();
diff --git a/assets/js/src/newsletters/send.jsx b/assets/js/src/newsletters/send.jsx
index 9b3dbafeeb..c7a55fab3d 100644
--- a/assets/js/src/newsletters/send.jsx
+++ b/assets/js/src/newsletters/send.jsx
@@ -101,27 +101,31 @@ define(
               return MailPoet.Ajax.post({
                 endpoint: 'sendingQueue',
                 action: 'add',
-                data: _.extend({}, this.state.item, {
-                  newsletter_id: this.props.params.id,
-                }),
+                data: {
+                  id: this.props.params.id
+                }
               });
             } else {
               return response;
             }
           }).done((response) => {
             this.setState({ loading: false });
-
-            if(response.result === true) {
-              this.context.router.push(`/${ this.state.item.type || '' }`);
-              MailPoet.Notice.success(response.data.message);
+            // redirect to listing based on newsletter type
+            this.context.router.push(`/${ this.state.item.type || '' }`);
+            // display success message depending on newsletter type
+            if (this.state.item.type === 'welcome') {
+              MailPoet.Notice.success(MailPoet.I18n.t('welcomeEmailActivated'));
+            } else if (this.state.item.type === 'notification') {
+              MailPoet.Notice.success(MailPoet.I18n.t('postNotificationActivated'));
             } else {
-              if(response.errors) {
-                MailPoet.Notice.error(response.errors);
-              } else {
-                MailPoet.Notice.error(
-                  MailPoet.I18n.t('newsletterSendingError').replace("%$1s", '?page=mailpoet-settings')
-                );
-              }
+              MailPoet.Notice.success(MailPoet.I18n.t('newsletterBeingSent'));
+            }
+          }).fail((response) => {
+            if (response.errors.length > 0) {
+              MailPoet.Notice.error(
+                response.errors.map(function(error) { return error.message; }),
+                { scroll: true }
+              );
             }
           });
         }
diff --git a/lib/API/Endpoints/SendingQueue.php b/lib/API/Endpoints/SendingQueue.php
index 7d30e838a3..8632b46378 100644
--- a/lib/API/Endpoints/SendingQueue.php
+++ b/lib/API/Endpoints/SendingQueue.php
@@ -1,5 +1,7 @@
 <?php
 namespace MailPoet\API\Endpoints;
+use MailPoet\API\Endpoint as APIEndpoint;
+use MailPoet\API\Error as APIError;
 
 use MailPoet\Mailer\Mailer;
 use MailPoet\Models\Newsletter;
@@ -14,29 +16,30 @@ use MailPoet\Util\Helpers;
 
 if(!defined('ABSPATH')) exit;
 
-class SendingQueue {
-  function add($data) {
+class SendingQueue extends APIEndpoint {
+  function add($data = array()) {
+    $id = (isset($data['id']) ? (int)$data['id'] : null);
+
+    // check that the newsletter exists
+    $newsletter = Newsletter::filter('filterWithOptions')
+      ->findOne($data['id']);
+
+    if($newsletter === false) {
+      return $this->errorResponse(array(
+        APIError::NOT_FOUND => __('This newsletter does not exist.')
+      ));
+    }
+
     // check that the sending method has been configured properly
     try {
       new Mailer(false);
     } catch(\Exception $e) {
-      return array(
-        'result' => false,
-        'errors' => array($e->getMessage())
-      );
-    }
-
-    // check that the newsletter exists
-    $newsletter = Newsletter::filter('filterWithOptions')
-      ->findOne($data['newsletter_id']);
-
-    if($newsletter === false) {
-      return array(
-        'result' => false,
-        'errors' => array(__('This newsletter does not exist'))
-      );
+      return $this->errorResponse(array(
+        $e->getCode() => $e->getMessage()
+      ));
     }
 
+    // Automated newsletters (welcome & post notification)
     if($newsletter->type === Newsletter::TYPE_WELCOME ||
        $newsletter->type === Newsletter::TYPE_NOTIFICATION
     ) {
@@ -45,133 +48,127 @@ class SendingQueue {
       $errors = $result->getErrors();
 
       if(!empty($errors)) {
-        return array(
-          'result' => false,
-          'errors' => $errors
-        );
+        return $this->errorResponse($errors);
       } else {
-        $message = ($newsletter->type === Newsletter::TYPE_WELCOME) ?
-          __('Your Welcome Email has been activated') :
-          __('Your Post Notification has been activated');
-        return array(
-          'result' => true,
-          'data' => array(
-            'message' => $message
-          )
+        return $this->successResponse(
+          Newsletter::findOne($newsletter->id)->asArray()
         );
       }
-    }
-
-    $queue = SendingQueueModel::whereNull('status')
+    } else {
+      // Standard newsletters
+      $queue = SendingQueueModel::whereNull('status')
       ->where('newsletter_id', $newsletter->id)
       ->findOne();
 
-    if(!empty($queue)) {
-      return array(
-        'result' => false,
-        'errors' => array(__('This newsletter is already being sent'))
-      );
-    }
+      if(!empty($queue)) {
+        return $this->errorResponse(array(
+          APIError::NOT_FOUND => __('This newsletter is already being sent.')
+        ));
+      }
 
-    $queue = SendingQueueModel::where('newsletter_id', $newsletter->id)
-      ->where('status', SendingQueueModel::STATUS_SCHEDULED)
-      ->findOne();
-    if(!$queue) {
-      $queue = SendingQueueModel::create();
-      $queue->newsletter_id = $newsletter->id;
-    }
+      $queue = SendingQueueModel::where('newsletter_id', $newsletter->id)
+        ->where('status', SendingQueueModel::STATUS_SCHEDULED)
+        ->findOne();
+      if(!$queue) {
+        $queue = SendingQueueModel::create();
+        $queue->newsletter_id = $newsletter->id;
+      }
 
-    if((bool)$newsletter->isScheduled) {
-      // set newsletter status
-      $newsletter->setStatus(Newsletter::STATUS_SCHEDULED);
+      if((bool)$newsletter->isScheduled) {
+        // set newsletter status
+        $newsletter->setStatus(Newsletter::STATUS_SCHEDULED);
 
-      // set queue status
-      $queue->status = SendingQueueModel::STATUS_SCHEDULED;
-      $queue->scheduled_at = Scheduler::scheduleFromTimestamp(
-        $newsletter->scheduledAt
-      );
-      $queue->subscribers = null;
-      $queue->count_total = $queue->count_to_process = 0;
+        // set queue status
+        $queue->status = SendingQueueModel::STATUS_SCHEDULED;
+        $queue->scheduled_at = Scheduler::scheduleFromTimestamp(
+          $newsletter->scheduledAt
+        );
+        $queue->subscribers = null;
+        $queue->count_total = $queue->count_to_process = 0;
+      } else {
+        $segments = $newsletter->segments()->findArray();
+        $segment_ids = array_map(function($segment) {
+          return $segment['id'];
+        }, $segments);
+        $subscribers = Subscriber::getSubscribedInSegments($segment_ids)
+          ->findArray();
+        $subscribers = Helpers::arrayColumn($subscribers, 'subscriber_id');
+        $subscribers = array_unique($subscribers);
+        if(!count($subscribers)) {
+          return $this->errorResponse(array(
+            APIError::UNKNOWN => __('There are no subscribers in that list!')
+          ));
+        }
+        $queue->status = null;
+        $queue->scheduled_at = null;
+        $queue->subscribers = serialize(
+          array(
+            'to_process' => $subscribers
+          )
+        );
+        $queue->count_total = $queue->count_to_process = count($subscribers);
 
-      $message = __('The newsletter has been scheduled');
-    } else {
-      $segments = $newsletter->segments()->findArray();
-      $segment_ids = array_map(function($segment) {
-        return $segment['id'];
-      }, $segments);
-      $subscribers = Subscriber::getSubscribedInSegments($segment_ids)
-        ->findArray();
-      $subscribers = Helpers::arrayColumn($subscribers, 'subscriber_id');
-      $subscribers = array_unique($subscribers);
-      if(!count($subscribers)) {
-        return array(
-          'result' => false,
-          'errors' => array(__('There are no subscribers in that list!'))
+        // set newsletter status
+        $newsletter->setStatus(Newsletter::STATUS_SENDING);
+      }
+      $queue->save();
+
+      $errors = $queue->getErrors();
+      if(!empty($errors)) {
+        return $this->errorResponse($errors);
+      } else {
+        return $this->successResponse(
+          Newsletter::findOne($newsletter->id)->asArray()
         );
       }
-      $queue->status = null;
-      $queue->scheduled_at = null;
-      $queue->subscribers = serialize(
-        array(
-          'to_process' => $subscribers
-        )
-      );
-      $queue->count_total = $queue->count_to_process = count($subscribers);
-
-      // set newsletter status
-      $newsletter->setStatus(Newsletter::STATUS_SENDING);
-
-      $message = __('The newsletter is being sent...');
     }
-    $queue->save();
+  }
 
-    $errors = $queue->getErrors();
-    if(!empty($errors)) {
-      return array(
-        'result' => false,
-        'errors' => $errors
-      );
+  function pause($data = array()) {
+    $id = (isset($data['id']) ? (int)$data['id'] : null);
+    $newsletter = Newsletter::findOne($id);
+
+    if($newsletter === false) {
+      return $this->errorResponse(array(
+        APIError::NOT_FOUND => __('This newsletter does not exist.')
+      ));
     } else {
-      return array(
-        'result' => true,
-        'data' => array(
-          'message' => $message
-        )
-      );
+      $queue = $newsletter->getQueue();
+
+      if($queue === false) {
+        return $this->errorResponse(array(
+          APIError::UNKNOWN => __('This newsletter has not been sent yet.')
+        ));
+      } else {
+        $queue->pause();
+        return $this->successResponse(
+          Newsletter::findOne($newsletter->id)->asArray()
+        );
+      }
     }
   }
 
-  function pause($newsletter_id) {
-    $newsletter = Newsletter::findOne($newsletter_id);
-    $result = false;
+  function resume($data = array()) {
+    $id = (isset($data['id']) ? (int)$data['id'] : null);
+    $newsletter = Newsletter::findOne($id);
 
-    if($newsletter !== false) {
+    if($newsletter === false) {
+      return $this->errorResponse(array(
+        APIError::NOT_FOUND => __('This newsletter does not exist.')
+      ));
+    } else {
       $queue = $newsletter->getQueue();
 
-      if($queue !== false) {
-        $result = $queue->pause();
+      if($queue === false) {
+        return $this->errorResponse(array(
+          APIError::UNKNOWN => __('This newsletter has not been sent yet.')
+        ));
+      } else {
+        $queue->resume();
+        return $this->successResponse(
+          Newsletter::findOne($newsletter->id)->asArray()
+        );
       }
     }
-
-    return array(
-      'result' => $result
-    );
-  }
-
-  function resume($newsletter_id) {
-    $newsletter = Newsletter::findOne($newsletter_id);
-    $result = false;
-
-    if($newsletter !== false) {
-      $queue = $newsletter->getQueue();
-
-      if($queue !== false) {
-        $result = $queue->resume();
-      }
-    }
-
-    return array(
-      'result' => $result
-    );
   }
 }
diff --git a/views/newsletters.html b/views/newsletters.html
index 624c40ea4a..d6af882c3f 100644
--- a/views/newsletters.html
+++ b/views/newsletters.html
@@ -210,19 +210,17 @@
     'saturdayMin': __('S'),
     'next': __('Next'),
     'previous': __('Previous'),
-
+    'newsletterBeingSent': __('The newsletter is being sent...'),
     'welcomeEmailActivated': __('Your Welcome Email is now activated!'),
     'welcomeEmailActivationFailed': __('Your Welcome Email could not be activated, please check the settings'),
     'postNotificationActivated': __('Your post notification is now active!'),
     'postNotificationActivationFailed': __('Your post notification could not be activated, check the settings'),
-
     'welcomeEventSegment': __('This newsletter is sent when someone subscribes to the list: "%$1s"'),
     'welcomeEventWPUserAnyRole': __('This newsletter is sent when a new WordPress user is added to your site'),
     'welcomeEventWPUserWithRole': __('This newsletter is sent when a new WordPress user with the role "%$1s" is added to your site'),
     'sendingDelayHours': __('%$1d hour(s) later'),
     'sendingDelayDays': __('%$1d day(s) later'),
     'sendingDelayWeeks': __('%$1d week(s) later'),
-
     'sendDaily': __('Send daily at %$1s'),
     'sendWeekly': __('Send weekly on %$1s at %$2s'),
     'sendMonthly': __('Send monthly on the %$1s at %$2s'),