ACP2E-2734: Emails are failing to send

Author: thiaramus

app/code/Magento/Sales/Model/EmailSenderHandler.php

@@ -105,6 +105,7 @@ public function __construct(
 
     /**
      * Handles asynchronous email sending
+     *
      * @return void
      */
     public function sendEmails()
@@ -137,6 +138,9 @@ public function sendEmails()
                             'email_sent'
                         );
                     } else {
+                        // When the email is failed to send, the email_sent attribute
+                        // should be set to false, preventing this email from being
+                        // sent over and over again in the next cron runs.
                         $this->entityResource->saveAttribute(
                             $item->setEmailSent(false),
                             'email_sent'

app/code/Magento/Sales/Test/Unit/Model/EmailSenderHandlerTest.php

@@ -256,6 +256,12 @@ public function testExecute(
                         ->expects($this->once())
                         ->method('saveAttribute')
                         ->with($collectionItem);
+                } else {
+                    $collectionItem
+                        ->expects($this->once())
+                        ->method('setEmailSent')
+                        ->with(false)
+                        ->willReturn($collectionItem);
                 }
             }
         }