This page provides an example for setting the
$wgSMTP configuration parameter if you would like to use a network internal SMTP relay accessible in your internal network for sending emails by your wiki.
$wgSMTP = [ 'host' => 'smtp-relay.mynetwork.int', 'IDHost' => '10.40.40.110', 'port' => 25, 'username' => null, 'password' => null, 'auth' => false ];
This example assumes that the relay is reached via the IP address and does not need additional authentication. Note that it may be required to explicitly allow the IP address of the respective server to relay via the host.