I am re-designing our company mail services, and we are migrating some mail-boxes to Google for Work. The objective is to have some users in the cloud, and some users on an on-premise Postfix server.
I have currently configured DNS with GMail MX records and configured GMail to forward all mail for unknown users to my Postfix server.
Whenever I send an e-mail from GMail (personal or business), the e-mail gets properly delivered to a correct Postfix mailbox. However, if I try to send e-mail from Postfix to GMail for Work user , I get an error message from Postfix.
Reporting-MTA: dns; glczwe-sp230001.ext.*filtered* X-Postfix-Queue-ID: AFB0A86F24 X-Postfix-Sender: rfc822; petr.balla@*filtered* Arrival-Date: Tue, 9 Feb 2016 20:43:48 +0100 (CET) Final-Recipient: rfc822; dl-cz-accounting@*filtered* Original-Recipient: rfc822;dl-cz-accounting@*filtered* Action: failed Status: 5.1.1 Diagnostic-Code: x-unix; user unknown
Obviously, Postfix handles the domain, so it rejects the e-mail, because the account does not exist locally. I know I could list all the users in /etc/postfix/transport, however I am trying to think of a way that would be easier from a mailbox provisioning perspective. Having to touch both mail-servers, GMail and Postfix when creating new users on a GMail servers is a bit of a pain for my taste.
Does anybody have an idea about a solution for my problem? I believe ith might be very common scenario for all Google for Work users.
The simplest solution is to run two mail servers on premise. One handles only incoming mail, while the other handles only outgoing mail and knows nothing of the first server.
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