How to change Postfix default smtp port to 2525

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article1

By default Postfix listens on Port 25. You can change it to any port. In our case, we would want to change it to 2525.

vi /etc/postfix/master.cf

Replace

smtp inet n - n - - smtpd

with

2525 inet n - n - - smtpd

Restart Postfix service.

systemctl restart postfix.service

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