This explains how large of an attachment you can have with ABetterOutlook.

The maximum allowed e-mail attachment size is 10MB.

In the computer industry e-mail is not a preferred method for large file transfers.  Most e-mail providers stick to a 2MB standard.  If you are dealing with files larger then 10MB inquire about FTP, SharePoint, or other file transfer methods.

An easy method to use is to go through sites like http://www.yousendit.com/  Where you e-mail a link to the recipient and they download it that way.