Hello Skaero,
Thanks for the input. In fact, I was able to achieve separate login url for each domain by just modifying /etc/httpd/conf/httpd.conf file.
DocumentRoot "/var/www/html" needs to be changed to
DocumentRoot "/var/www/roundcube-0.2.1"
This is working perfectly fine, now I can login to each domain with mail.domain1.com , mail.domain2.com, etc.
Here problem is login page for each domain will look similar. I want separate page content for each domain. Any pointer on how I can achieve this?
Please keep in mind that I am very very new to linux, web server, roundcube, etc