"With Gmail, you can send and receive messages up to 25 megabytes (MB) in size. Please note that you may not be able to send larger attachments to contacts who use other email services with smaller attachment limits. If your attachment bounces, you should invite them to Gmail," suggests Google.
For some reason, Gmail's Flash uploader doesn't allow me to upload files that are larger than 10 MB. The error message is "attachment failed" and Google's suggestions aren't very helpful. Switching to the basic uploader in the settings solves the problem, but it's more tedious to upload multiple files.
{ Thanks, Ben. }