SMTP 4xx and secondary MX record as a way to redirect mail

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http://serverfault.com – I have a domain that uses Google Apps for mail. Now I decided to set up my own MTA (Postfix) on VPS (running Debian squeeze). There is only a very small number (less than half a dozen) of users and some of them prefer to keep using GMail web interface (and the rest of them have local Unix accounts). So I need to relay mail for certain recipients to Google SMTP servers. At first I did the following: Added altmail.mydomain.org domain alias in Google Apps. Added Postfix virtual aliases for users that want GMail: user [email protected] Set up transport table: altmail.mydomain.org (HowTos)