Hi Philip, I used YAHOO as just an example, it could be any SMTP, VSNL, HOTMAIl etc. But ur last part did anser my question. The recving SMTP will do a MX lookup and upon not able to find the respectibve IP it will dump it to the local SMTP postmaster. Thanks. --Sandeep
I'm assuming that yahoo blocks non-existent domains from sending mail.
It depends on how the mail is being sent. If your smtp server connects directly to yahoo's smtp server then the mail will be rejected before it even leaves your machine. Not because the destination account does not exist, but because the source domain does not exist.
If you send your mail through a smart host, then it depends on how your smart host is configured. If it is configured to block non-existent domains, then same problem. If non-existent domains are allowed to connect, then the mail will go to your smart host, but will be rejected from yahoo.
Now, assuming that the mail has in fact managed to get out of your system, and got somewhere - either your smart host, or yahoo. It will bounce for one of the two reasons. Where does it bounce to?
The server that is bouncing the mail will basically do a MX lookup for the destination domain (aaaaa.com), but will not find it. It will realise that it cannot return the mail, so will check what it is configured to do in such cases. In most cases, it would be configured to bounce the mail to a postmaster in its own domain, and this it what it does.
Does that answer your question?
Philip
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