How can we make mail server on Linux and anyone can tell that Squid 2.6 is stable or 3.1 thanks

You can use sendmail or qmail for email services

I've used sendmail, postfix, qmail, zimbra mail. All of them are very good. Now a days, zimbra mail giving lot of email features comparing to other mail systems and it is easy to use also. You can import emails from Exchange server to Zimbra email connectors. Let me know if you need more information about setup and installation.

 

Squid Stable versions are below

VersionFirst STABLE release DateLatest ReleaseLatest Release Date3.4 09 Dec2013 3.4.12 18 Feb2015 3.3 09 Feb2013 3.3.13 28 Aug2014 3.2 14 Aug2012 3.2.13 13 Jul2013 3.1 29 Mar2010 3.1.23 09 Jan2013 3.0 13 Dec2007 STABLE26 28 Aug2011 2.7 31 May2008 STABLE9 16 Mar2010 2.6 01 Jul2006 STABLE23 17 Sep2009 2.5 25 Sep2002 STABLE14 20 May2006 2.4 20 Mar2001 STABLE7 02 Jul2002

here this will help

http://flurdy.com/docs/postfix/

use http://www.qmailtoaster.com/ for mail server installation and setup. Its step by step guideline to setup mail server. 

 

3.4 squid is stable release.