Adding the SMTP port 25 in squid.conf?

I want to add port 25 in my Squid proxy server to access e-mail to Whts are steps to edit squid.conf plz tell me

I'm not as familiar with Linux, but to save some frustration, let me say this: Some ISPs block port 25 is open in order to reduce spam. Nothing to do about it, but switch ISPs to fix that. So if you feel you've done everything right, but the work is still usual to find that, by telnet to telnet: / / [youremailserver]: 25 If you do not get an answer, is because your ISP blocks port at its end.