Message Queue

Im having the same problem. There is one email that wont send... Its a shipment sent email...
I got this error in the log.
But test email address works and testing the message template works. Aggravating!

System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: 5.1.1 The email account that you tried to reach does not exist. Please try at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, Boolean allowUnicode, SmtpFailedRecipientException& exception) at System.Net.Mail.SmtpClient.Send(MailMessage message) at Nop.Services.Messages.EmailSender.SendEmail(EmailAccount emailAccount, String subject, String body, String fromAddress, String fromName, String toAddress, String toName, String replyTo, String replyToName, IEnumerable`1 bcc, IEnumerable`1 cc, String attachmentFilePath, String attachmentFileName, Int32 attachedDownloadId, IDictionary`2 headers) at Nop.Services.Messages.QueuedMessagesSendTask.Execute()

This is a recipient error:
RecipientException: Mailbox unavailable. The server response was: 5.1.1 The email account that you tried to reach does not exist.

Have you tried using your regular email client to send an email to that email address?

New York wrote:

OK, thanks for the reply... Thats something I didnt consider.. I will have to call them during business hours and check the email address. We corresponded before, but not within the last month. Maybe he quit that job?

Does anybody know what this error is?
NOP 3.90
Im using G Suite for my emails and Godaddy as the email server and my site is hosted with appliedi. LOL

Full message  
System.Net.Mail.SmtpException: Error in processing. The server response was: 4.3.0 Multiple destination domains per transaction is unsupported. Please at System.Net.Mail.RecipientCommand.CheckResponse(SmtpStatusCode statusCode, String response) at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, Boolean allowUnicode, SmtpFailedRecipientException& exception) at System.Net.Mail.SmtpClient.Send(MailMessage message) at Nop.Services.Messages.EmailSender.SendEmail(EmailAccount emailAccount, String subject, String body, String fromAddress, String fromName, String toAddress, String toName, String replyTo, String replyToName, IEnumerable`1 bcc, IEnumerable`1 cc, String attachmentFilePath, String attachmentFileName, Int32 attachedDownloadId, IDictionary`2 headers) at Nop.Services.Messages.QueuedMessagesSendTask.Execute()

In your default email account settings, what do you have for Host?  (smtp.gmail.com  ?)

New York wrote:

I have the google host: aspmx.l.google.com

Now when sending a test message, it sends to any gmail account [email protected]. But not any other account. Like one of my other email accounts [email protected]

You might want to try to use smtp.gmail.com in place of aspmx.l.google.com.

Configure like this
https://www.nopcommerce.com/boards/t/23569/solved-551-authentication-required-with-smtpgmailcom.aspx?p=2#183996

Be sure your gmail password is strong.  You may need to adjust your gmail account settings also mentioned in the above post.

What ended up working was advise from my hosting provider appliedi.net.

In the webmail, Change the host to smtp.gmail.com, change the port to 587 and tick SSL... THATS ALL

Now it sends to all email addresses. I didnt do anything else in Gmail.