Can't https://mailserver.example.com even with VPN connected

[salu]

Hi,

I just reinstalled ZCS Ubuntu 6.06 LTS x86_64 without proxing and archiving features.

After installation, somehow I can't https my webmail box either through IP address, or server name, even with VPN connected. But with VPN connected, I can still https://servername.example.com:7071/zimbraAdmin and http://servername.example.com. I didn't change any setting in my firewall configuration.

With previous installation, I was able to https my webmail through IP address without VPN connected.

How should I debug this problem?

Thanks!
Richard