See !!?
He's an alien !!!!!
Now, for being serious:
The trick fro the relay SMTP is to set all the "my_networks", "my_destinations" ,etc... in a proper way.
The Postfix documentation is very rich about it.
Check "smtpd_recipient_restrictions = " parameters.
I.e.:
smtpd_client_restrictions = permit_mynetworks
smtpd_sender_restrictions = permit_mynetworks
The meaning of all this initial difficulties is NOT allowing accidental misuse of your SMTP server by spammers.
USEFUL COMMENTS I FOUND GOOGLEING:
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The simplest form of relay control is accept mail for relay only from IP addresses owned by your organization, or otherwise known to be trustworthy.
mynetworks = 127.0.0.0/8 192.0.34.0/8
relay_domains =
smtpd_recipient_restrictions = permit_mynetworks, reject_unauth_destination, permit
The permit_mynetworks restriction returns PERMIT if the IP address of the connecting client matches an IP address in $mynetworks. The reject_unauth_destination returns REJECT if the destination is not the local machine or a member of $relay_domains.
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If your ISP is filtering traffic on port 25, thus blocking you from sending outgoing mail, and so you want to configure your mailserver to relay all your mail out through your ISP's server, like they want you to. If you're running postfix, this turns out to be very easy -- in /etc/postfix/main.cf, just set the variable:
relayhost = smtp.yourisp.com
then restart postfix (/etc/init.d/postfix restart, as root).
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More:
http://www.metaconsultancy.com/whitepapers/smtp.htm
http://www.redhat.com/support/resour...OWTO/x368.html