IP table rule for redirect gmail to other url

Hi all.......
I installed squid transparent proxy in my office and is working fine.
But the problem is that, all the mails are blocked but if any one using https: then gmail will work. I tried the iptable rule for blocking gmail then our office mail is also not working (tied with google). What I want to do is block gmail from http and https or redirect the traffic to/from gmail to webmail.xxxxxx.com.
Pls help me......

Thanks in advance

Saju

This is not the job of IPTABLES. IPTABLES works on IP Addresses not URL's. And DNS also doesn't do URL's before you walk down that line. Your proxy might be able to do what you are looking for. Google it.

proxy it with squid ;)