Forgetting to add the attachment to the email. Everybody does it.

An adjustment to your workflow when sending files via email (eg Right Click - Send to Mail Recipient on PC, I use Quicksilver on my MAC) can help negate the problem somewhat but I have a suggestion (maybe others have had it too) for what I think is a killer mail client feature.

Upon clicking the "Send" button the program should scan the body (and perhaps subject) of the message looking for key words like "attached", "attachment", "files", "included" etc. If these words a present and there is no file attached the system could present a polite dialogue asking if the user is in deed attempting to send an attachment. If the user is they have a chance to add the file and prevent both the minor embarrassment and time wasting hassle for both themselves and the recipient.

Can't see that being too hard to do. Surely even web mail solutions could do it with all that AJAX action happening.