Knowledgebase: SMTP Server (Outgoing)
Why do I get a returned email?
Posted by Roy Petersen on Feb-15-2007 12:16 PM
This error usually occurs when the recipient(s) of one or more of your e-mail messages has an invalid e-mail address.

For example, if you forget to put an "@" in the e-mail address, the SMTP server will automatically reject this and will not send the e-mail message. You will need to go through the recipient or recipients of your e-mail message to make sure the syntax (username@yourdomain.com) is correct.
This is not the only reason mail might be undeliverable. When you receive the returned mail, there should be some details in the message you receive that explain why it was returned. If you think the 'bounce' is in error, or need help determining the reason, please open a help desk ticket and paste the entire bounced message in it, including all headers.