Application Development Software

I have setup beehive server (over linux) and the installation went successful. Even i am able to access email accounts via the zimbra webclient. However when i try to configure thunderbird or zimbra desktop client to access the same mail account both return error saying "could not connect to mail server; the connection was refused".
There is a proxy server setup in the LAN here and i have put the server IP in the ignore list still i get the same error (firewal and antivirus are also turned off). Any suggestions what might be wrong with my setup?

Thanks.