I have two local SMTP servers, one is running on port 25 and the other is running on port 2525.

When i use heirloom mailx to send out email, it uses the local SMTP server on port 25. However, i wanted mailx to use local SMTP server on port 2525 instead. So, i edited the system wide configuration file /etc/mail.rc and added in the line "set smtp=127.0.0.1:2525". So now mailx is successfully able to use smtp server on port 2525 instead of smtp server on port 25 to deliver emails.