Similar to programs used to get Hotmail over pop3, someone has come up with a program allowing users to do the same with Gmail.
Essentially, the program acts as a "local mail server", which your email client connects too. The program connects to gmail, downloads your emails, and converts them such that Outlook / Thunderbird is none the wiser.
A nice program that brings webmail to the desktop, it"s being offered free and can be found below. If you like it, don"t forget to show your grattitude to the developer :)