What makes you think you can't? AOL supports 16MB attachments, although recipient ISPs may have lower limits.
If your attachment is bigger then approx. 12MB you can still send/share this file by using the xdrive service which is integrated with webmail. It's in beta only right now. You need to be using http://beta.webmail.aol.com. More information at
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them