Mail Composer: Draft not deleted when sending

[benbucksch]

Reproduction

1. Write new mail (using IMAP account)
2. Type content, subject
3. Click [Save] button on top right
4. Go to folder "Drafts"
5. Click [Edit Draft]
6. [Send]
7. Go to folder "Drafts"

Actual result

The draft is still here

Expected result

The draft has been deleted

Other circumstances

1. Open a draft
2. Change the subject
3. [Save] in composer
4. Check "Drafts" folder
5. -> The older draft has been deleted - as expected
6. -> It fails only during send

[NeilRashbrook]

As far as I can tell, any email in the email composer has a folder, which used to always be the Drafts folder (as set in MailAccount.newMailFrom).

Commit 521b168 changed that for replies so that the email's folder is the desired sent folder. Unfortunately that only works for emails that are replied and immediately sent.

As such, what you appear to be seeing is actually the sent message. At least, I think it is; I'm confused by the message-id changing each time the message is saved or sent, and also by a very dodgy getDraftOnServer function.