Setting up a forwarding-only email server

Solution 1:

The telnet session and the postfix logs do not appear to be doing the same thing.

The 'RCPT TO' should be the local user, not the gmail user.

The 'MAIL FROM' is also different, since in the second, you appear to be the local user, and in the first, you're a gmail user.

So the telnet session is not a valid test.

The logs indicate that google has accepted the email. Check your spam tag again.

Solution 2:

Are you sending the test E-Mail from gmail? Over at Laughing Squid Web hosting we find that gmail does not like forwarded E-Mail if it is sent from gmail and then forwarded to gmail. It seems to do with its spam filter. I would suggest trying with yahoo and see what happens then.