Removing mail attachments - workaround
I can't believe that Apple hasn't fixed this yet, or that someone out there hasn't written a script or app to remove attachments from sent mail. It's apparently not a high priority for Apple. I have found a workaround, however, that works really well for me.
Whenever I send mail with large attachments, I leave them in my sent folder. When I receive emails with attachments, I always remove the attachment before deleting the message. I like to keep my Trash folders handy because I occasionally need to search through my trash for information, but I don't want my Trash folder (or Sent folder) filled with large attachments that I already have somewhere else on my computer. For me, I just need a record that <filename> was sent to <so-and-so> on <date>. I don't want copies of the actual attachments in my Mail folders.
Once a month or so, when I receive a message with an attachment, I'll move it to my Sent folder. Then, I can select it and all of the other sent mail with attachments and remove all of the attachments before moving all of those messages to the Trash. It's not elegant, but it works.
MacBook Pro, Mac OS X (10.7.5), iPad, iPhone 4, BlackBook, iPod