For the past several releases, Mail.app has had a problem where it creates multiple offline drafts of a message that stick around after the message is sent successfully. Usually, I just clean them out when I spot them, no big deal.

Today it happened with a message that contained a number of rather large binary attachments (~30 megabytes), which I was sending to my Sony Tablet as a test. The test went fine at the office, but when I got home and plugged my computer in, the Internet went away.

Mail.app was frantically trying to upload four copies of the huge draft message to my IMAP server, and completely saturating my uplink. The only way to fix it was to force-quit Mail and empty out the contents of the .OfflineCache directory for that account. This was, of course, not the first solution I tried. Grrr.