Changing SMTP Port to 587 (ISP Blocking and SASL)

March 31, 2009 at 12:27 am · Filed under Uncategorized

I got tired of ISPs blocking outgoing port 25, so I moved our SMTP for clients to port 587. Unfortunately, when migrating our new server, I couldn’t remember how to do this.

After some Googling, I found the answer; add this line in /etc/postfix/master.cf, substituting your port number for 25000:

25000 inet n - n - - smtpd -o smtpd_sasl_auth_enable=yes

I left port 25 on too, so users can try either from their ISP. If you want to turn off port 25, just comment out this line:

smtp    inet    n       -       n       -       -       smtpd -o smtpd_sasl_auth_enable=yes

Remember to open up the port in your server firewall as well!

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