How to setup Postfix to send mail 'from' any_address@mydomain.com using Google Apps?

Question

I have a Postfix mail server set up. I have one account credentials entered in. The mail server is sending mail through the Google Apps mail servers. So in a postfix config file I have my gmail credentials as:

test@mydomain.com
mypassword

In my PHP application I use the mail() function to send mail.

Everything works, except no matter what I set the 'from' header address to, it ALWAYS says it is coming from test@mydomain.com.

I have used other setups where the email's 'from' header could be altered, so that I could have support@mydomain.com, noreply@mydomain.com, etc..

Any help would be greatly appreciated in how to set this up.

Answer 1

You can't change that at the Postfix level. Postfix already does what you want. Google replaces the sender with the authorized account. This is a "feature" of Google Apps to disallow the forging of senders.

Edit: If you don't change Google Apps, then you have to change Postfix' behavior.

In main.cf edit or add:

sender_dependent_relayhost_maps = hash:/etc/postfix/sender_relayhost
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/smtp_relayhost_auth
smtp_sasl_security_options = noanonymous
smtp_sender_dependent_authentication = yes

in /etc/postfix/sender_relayhost put:

user1@mydomain.com          [aspmx.l.google.com]
user2@mydomain.com          [aspmx.l.google.com]

in /etc/postfix/smtp_relayhost_auth put

user1@mydomain.com      user1@mydomain.com:mypassword
user2@mydomain.com      user2@mydomain.com:hispassword

and so on.