I am not sure what function I need in this situation, or how to configure it...
I have many domains, with email accounts me@mydomain1, me@mydomain2, I set my domains to have my one mail server (which is a separated / dedicated domain) by MX record, so that one mail server can fetch all my email accounts.
In that mail server I have postfix and I set it to forward most of my email accounts to my @gmail, this is done by postfix's virtual domains mapping function.
Problem is: many times, when external sender sends me an email, gmail says that the IP of my postfix mail server is not allowed to send email for that external sender. So gmail rejects it.
Edit: by "external sender" I mean any stranger/user trying to contact me, e.g from a @yahoo address.
Does this mean I need to configure postfix as a relay ? If so, without many details, what postfix functions/options should I look into ?
