So you want to be able to do ETRN with Postfix. Not a problem.
Open up main.cf and add a few lines:
transport_maps = hash:/usr/local/etc/postfix/transport
smtpd_recipient_restrictions = permit_mx_backup, permit_mynetworks, check_relay_domains
relay_domains = /usr/local/etc/postfix/relay-domains
fast_flush_domains = /usr/local/etc/postfix/relay-domains
The recipient_restrictions line is the default except with the addition of "permit_mx_backup" which allows
our own server to be in the MX list without directly expecting to be the last stop for the mail.
Then we need to create a /usr/local/etc/postfix/relay-domains and put in a comma delimited list of
all the domains we want to recieve ETRN mail for.
Now create a file called "transport" and make it look like this:
targetdomain.com hold:[target_smtp_server_name]
Then
postmap hash:transport
in order to rebuild the hash file for the transports. Finally we'll need to alter the MX records in the DNS for the domain
to look like:
MX 0 target_smtp_server_name.
MX 10 our_ETRN_server_name.
You're done!
postfix reload
and enjoy!
