The maximum size of email files that can be sent appears to me to be a mystery.
It is no mystery, email itself (as in the protocols used) can handle any size file you like - however most ISP's will restrict the size you can send/receive so as not to affect server performance (e.g. consuming diskspace and resources tied up with the transmission).
A company I used to work for produced
Interoute Express | Welcome - which is a tooltray applet and is free. It integrates with the explorer shell, allowing you to right click and and send to... email via interoute express - this basically opens an email and puts a link in the page whilst the tooltray app uploads to the server for later download - the link will remain valid for one month before the file is purged.