Mac Mail connection to Microsoft Exchange 2007

[gilesbrading]

Here are the facts:

OSX Lion
Mac Mail 5.0 - Microsoft Exchange Account

Connecting to office VPN successfully
Can ping Microsoft Exchange Server I/P address successfully through terminal.
Trying to connect to Microsoft Exchange Server 2007 Service Pack 1 Roll Up 4
I am told by my IT department that the Internal Server is named: exchangeserver
I have selected do not use SSL.


ERROR
The server returned the error: The server “exchangeserver” cannot be contacted on port 80.

Please can anyone help. Does the server name seem right in it's format?

Thanks in advance

Giles