relay_domains
This parameter restricts what client hostname domains (and subdomains thereof)
this mail system will relay mail from, and restricts what destination domains
(and subdomains thereof) this system will relay mail to.
By default, Postfix relays mail:
- from trusted clients whose IP address matches $mynetworks,
- from trusted clients matching $relay_domains or subdomains thereof,
- from untrusted clients to destinations that match $relay_domains
or subdomains thereof, except addresses with sender-specified routing.
The default relay_domains value is $mydestination.
In addition to the above, the Postfix SMTP server by default accepts mail
that Postfix is final destination for:
- destinations that match $inet_interfaces,
- destinations that match $mydestination
- destinations that match $virtual_maps.
Specify a list of hosts or domains, /file/name patterns or
type:name lookup tables, separated by commas and/or whitespace. A file
name is replaced by its contents; a type:name table is matched when a
(parent) domain appears as lookup key.
NOTE: Postfix will not automatically forward mail for domains that list this
system as their primary or backup MX host. See the permit_mx_backup
restriction, in the description of the smtpd_recipient_restrictions
parameter.