I have set up an alias in /etc/mail/aliases like this:
This relay DOES work when I telnet to example.com 25 and send mail to email@example.com (where example.com is my domain); it indeed turns up in firstname.lastname@example.org inbox.
Also mail sent from my server at example.com is generally deliverable to this same email address, email@example.com.
HOWEVER, the relay DOES NOT work when I send mail from firstname.lastname@example.org to email@example.com, expecting it to be relayed back to firstname.lastname@example.org.
The mail.log shows it being received and sent just fine, so I guess it is being blocked by gmail for some reason. Why though? As I said, gmail generally does except mail from this server.