Mail, Snow Leopard, Server connect problems

First, I couldn't get Thunderbird 14.0 email to work with 10.5.8 Snow Leopard iMac. My server is Comcast. At least 10 hours put into multiple tech suggestions.

So I decided to connect up Mail at last. Mail is 3.6.

2 1/2 hours with a Comcast chat box tech and no go. They said to contact Apple.

Must I upgrade to Lion in order to use Mail? Must I update Lion and Mail to use Mail?

Thanks.