I've recently configured Zimbra to forward a copy of all incoming/sent mails to an archiving server (mailpiler).
When I check the mails received on the bcc host, I can see thousands of spams archived, all these spams are sent to a non-existing user in my Zimbra.
So basically, Zimbra rejects emails sent to unlisted recipient (smtpd_reject_unlisted_recipient=yes in main.cf), but these mails are still forwarded via the always_bcc parameters and can make it to my archiving server.
Seems like they are forwarded straight away and these mails does not pass into the 'unlisted_recipient' check.
Is there a way to correct it?
Thanks in advance.
Update : I managed to figure out "why" this happens :
-A copy of all incoming mails is forwarded to a known host (my archiving server) via the always_bcc parameter.
-The mail passes the "unlisted_recipient' check since the mail is sent to a known host
-My archiving server stores the email using the TO: header, which, in this case, is replaced with a unknown user, that's why I can see mails sent to unknown user making it to my archiving server..
I still haven't figured out how to solve the problem, any advice?