services.postfix.settings.main.relayhost

List of hosts to use for relaying outbound mail.

Putting the hostname in angled brackets, e.g. [relay.example.com], turns off MX and SRV lookups for the hostname.

https://www.postfix.org/postconf.5.html#relayhost

Type
null or (list of string)
Default
[ ]
Example
[
  "[relay.example.com]:587"
]
Declared
<nixpkgs/nixos/modules/services/mail/postfix.nix>