[BKB]

Originally posted by ivec
I think there are several reasons. The first one is that there was never a great demand for this since IMAP was not very popular. Those who needed to clear their mailboxes from big attachments would either delete the whole message, hack around it themselves or use IMAPSize (the latter allows you to strip attachments from multiple messages in one go).

Second, IMAP doesn't (yet) provide attachment deletion as a protocol feature which makes people think it is not possible.

Third and most important, almost all email clients today still treat messages from IMAP stores in the old POP way (TB was one of them until recently). When you open a message for viewing they download the whole message with all attachments. So, imagine wanting to delete a 10MB attachment, your client would have to download the whole lot, do some MIME reordering and processing (the POP way - on the whole message) and upload a stripped message. Not very effective. IMAP works differently, it provides nice ways for clients to download only message parts that they really need. The hard thing about this is that MIME parsing can't be done on the whole message, it has to be done by processing body structure replies from IMAP servers which is not trivial. And in order for a client to perform this operation it has to have a solid IMAP framework which TB now does.

Pretty cool, thanks for the explanation.