I know I'm a lot late to this discussion, but here's the definitive answer.
Agent Office requires a MAPI compliant e-mail client. It's not too important to know what MAPI stands for. You just need to know that there are a limnited number of alternatives that meet this requirement. Outlook, Thunderbird and Eudora are the best of them. No web-mail program will work - not gmail, not ymail, not AOL, not even the web-based version of Outlook. Basically, if it doesn't use POP3 and SMTP to communicate, it can't talk to Agent Office.
That being said, if you have a PDA that can sync with GMail, you may be able to use AO's intellisync to link it to your Agent Office, but that would be enormously tedious.
Your Internet Service Provider (ISP) probably offers you a POP3 e-mail account free with the service. Get this set up and activated, then forward your GMail account to it. Then you can link Agent Office to your ISP's e-mail, and everything will work just fine.
Rgds
Pluschap.
PS For FREE Agent Office help, sign on to the Agent Office Users Group forum at http://www.lusby.org/AventOffice