Knowledgebase: SMTP Server (Outgoing)
Why do e-mail messages I send out to people bounce back to me?
Posted by Roy Petersen on Feb-15-2007 12:16 PM
There are many reasons this can happen, but e-mail "bounces" back to the sender usually under 3 conditions:
  1. The domain of the recipient's e-mail address does not exist
  2. The e-mail address of the recipient no longer exists
  3. The SMTP server of the recipient's domain was not reachable for a long period of time.

By "bouncing", your original e-mail message comes back into your Inbox along with a standard error message produced by the SMTP server. This error message should give you a good indication of the problem.