- Adds methods to format mailer send/connection succes & error results

- Updates all mailing methods to return true on success and error message
  on failure

lib/Mailer/Mailer.php

@@ -154,4 +154,26 @@ class Mailer {
     // bse64_encode non-ASCII string as per RFC 2047 (https://www.ietf.org/rfc/rfc2047.txt)
     return sprintf('=?utf-8?B?%s?=', base64_encode($name));
   }
+
+   static function formatMailerConnectionErrorResult($error_message) {
+    return array(
+      'response' => false,
+      'action'=> 'connect',
+      'error' => $error_message
+    );
+  }
+
+  static function formatMailerSendErrorResult($error_message) {
+    return array(
+      'response' => false,
+      'action'=> 'send',
+      'error' => $error_message
+    );
+  }
+
+  static function formatMailerSendSuccessResult() {
+    return array(
+      'response' => true
+    );
+  }
 }

lib/Mailer/Methods/AmazonSES.php

@@ -1,6 +1,8 @@
 <?php
 namespace MailPoet\Mailer\Methods;
 
+use MailPoet\Mailer\Mailer;
+
 if(!defined('ABSPATH')) exit;
 
 class AmazonSES {
@@ -48,10 +50,17 @@ class AmazonSES {
       $this->url,
       $this->request($newsletter, $subscriber)
     );
-    return (
-      !is_wp_error($result) === true &&
-      wp_remote_retrieve_response_code($result) === 200
-    );
+    if(is_wp_error($result)) {
+      return Mailer::formatMailerConnectionErrorResult($result->get_error_message());
+    }
+    if(wp_remote_retrieve_response_code($result) !== 200) {
+      $response = simplexml_load_string(wp_remote_retrieve_body($result));
+      $response = ($response) ?
+        $response->Error->Message->__toString() :
+        sprintf(__('%s has returned an unknown error.', 'mailpoet'), Mailer::METHOD_AMAZONSES);
+      return Mailer::formatMailerSendErrorResult($response);
+    }
+    return Mailer::formatMailerSendSuccessResult();
   }
 
   function getBody($newsletter, $subscriber) {

lib/Mailer/Methods/MailPoet.php

@@ -1,6 +1,8 @@
 <?php
 namespace MailPoet\Mailer\Methods;
 
+use MailPoet\Mailer\Mailer;
+
 if(!defined('ABSPATH')) exit;
 
 class MailPoet {
@@ -21,10 +23,16 @@ class MailPoet {
       $this->url,
       $this->request($message_body)
     );
-    return (
-      !is_wp_error($result) === true &&
-      wp_remote_retrieve_response_code($result) === 201
-    );
+    if(is_wp_error($result)) {
+      return Mailer::formatMailerConnectionErrorResult($result->get_error_message());
+    }
+    if(wp_remote_retrieve_response_code($result) !== 201) {
+      $response = (wp_remote_retrieve_body($result)) ?
+        wp_remote_retrieve_body($result) :
+        wp_remote_retrieve_response_message($result);
+      return Mailer::formatMailerSendErrorResult($response);
+    }
+    return Mailer::formatMailerSendSuccessResult();
   }
 
   function processSubscriber($subscriber) {

lib/Mailer/Methods/PHPMail.php

@@ -1,6 +1,8 @@
 <?php
 namespace MailPoet\Mailer\Methods;
 
+use MailPoet\Mailer\Mailer;
+
 if(!defined('ABSPATH')) exit;
 
 class PHPMail {
@@ -19,9 +21,13 @@ class PHPMail {
       $message = $this->createMessage($newsletter, $subscriber);
       $result = $this->mailer->send($message);
     } catch(\Exception $e) {
-      $result = false;
+      return Mailer::formatMailerSendErrorResult($e->getMessage());
     }
-    return ($result === 1);
+    return ($result === 1) ?
+      Mailer::formatMailerSendSuccessResult() :
+      Mailer::formatMailerSendErrorResult(
+        sprintf(__('%s has returned an unknown error.', 'mailpoet'), Mailer::METHOD_PHPMAIL)
+      );
   }
 
   function buildMailer() {

lib/Mailer/Methods/SMTP.php

@@ -1,6 +1,8 @@
 <?php
 namespace MailPoet\Mailer\Methods;
 
+use MailPoet\Mailer\Mailer;
+
 if(!defined('ABSPATH')) exit;
 
 class SMTP {
@@ -33,9 +35,13 @@ class SMTP {
       $message = $this->createMessage($newsletter, $subscriber);
       $result = $this->mailer->send($message);
     } catch(\Exception $e) {
-      $result = false;
+      return Mailer::formatMailerSendErrorResult($e->getMessage());
     }
-    return ($result === 1);
+    return ($result === 1) ?
+      Mailer::formatMailerSendSuccessResult() :
+      Mailer::formatMailerSendErrorResult(
+        sprintf(__('%s has returned an unknown error.', 'mailpoet'), Mailer::METHOD_SMTP)
+      );
   }
 
   function buildMailer() {

lib/Mailer/Methods/SendGrid.php

@@ -1,6 +1,8 @@
 <?php
 namespace MailPoet\Mailer\Methods;
 
+use MailPoet\Mailer\Mailer;
+
 if(!defined('ABSPATH')) exit;
 
 class SendGrid {
@@ -20,13 +22,17 @@ class SendGrid {
       $this->url,
       $this->request($newsletter, $subscriber)
     );
-    $result_body = json_decode($result['body'], true);
-    return (
-      !is_wp_error($result) === true &&
-      !preg_match('!invalid!', $result['body']) === true &&
-      !isset($result_body['errors']) === true &&
-      wp_remote_retrieve_response_code($result) === 200
-    );
+    if(is_wp_error($result)) {
+      return Mailer::formatMailerConnectionErrorResult($result->get_error_message());
+    }
+    if(wp_remote_retrieve_response_code($result) !== 200) {
+      $response = json_decode($result['body'], true);
+      $response = (!empty($response['errors'])) ?
+        $response['errors'] :
+        sprintf(__('%s has returned an unknown error.', 'mailpoet'), Mailer::METHOD_SENDGRID);
+      return Mailer::formatMailerSendErrorResult($response);
+    }
+    return Mailer::formatMailerSendSuccessResult();
   }
 
   function getBody($newsletter, $subscriber) {