SquirrelMail Login - login.php pop-up

On my (once again re-installed) test-setup Debian Squeeze SquirrelMail Login acts bit strange (to me).

I have web-server example.com (no SSL) and mail-domain example.com

I have followed 20.2 (but stopped before virtual host not made)
http://www.howtoforge.com/perfect-server-debian-squeeze-with-bind-and-courier-ispconfig-3-p6

What is working (i.e. going to login page was not working before 20.2)
- ISPConfig3 quick-link from email - mailbox e.g. "http://www.excample.com:8080/mail/webmailer.php?id=1 goes to http://server1.excample.com/webmail/src/login.php
- any link http://XYZ.example.com/webmail or just AYZ.example.com/webmail (XYZ can be anything

But If I enter only domain name
- http://excample.com works (www page)
- http://excample.com/webmail

I'l get new window with

Not a biggest thing, but if someone uses webmail and get that message, does not look nice...

Any advice what to check?

 

Still don't know what was the issue, but now running w/o that problem after changing to roundcube by following
http://www.howtoforge.com/easy-roundcube-over-ssl-and-webmin-with-fail2ban-for-ispconfig-3-on-debian-squeeze