Why Do I Have Duplicate Items In Drafts Folder When Using IMAP?
One relatively common problem people who use Mac Mail have reported to us, is that the program will seem to collect multiple copies in its Drafts folder when you are using an IMAP mail box. The way Mail handles draft messages is that a local draft folder is created on your computer where these messages are automatically saved when you start composing. If you do not save them directly, they will stay there until the message is either sent or discarded without being saved. If you do purposefully save them, they will be removed either upon being sent or otherwise only if you remove them manually.
If you use IMAP email accounts, Mail may automatically enable the option to save a copy of these draft messages in a corresponding drafts folder on the IMAP server. Any changes to the local drafts folder will be synchronised to the server so you can access your drafts from alternate email clients, such as Webmail, another computer, or a mobile device.
This problem happens for IMAP accounts, and seems to happen when people have Mail store draft messages on the server. Each time the computer does a send and recieve sweep (typically every 5 minutes or so) a new copy of the draft will be saved.
Solution / Workaround - Disable Server Draft Mailboxes
The solution is to only use a local copy of your drafts, so that the copies are not uploaded to the server for synchronisation with other devices connected to this account. Unfortunately this means you will no longer be able to start composing a message on one computer and then complete it on another, if you still need that feature but can't live with the multiple drafts you may need to consider switching to another mail client like Thunderbird or our Webmail facility.
To disable this 'feature', go to Mail's preferences, select your email account, go to the Mailbox Behaviours tab and uncheck the option to store draft messages on the server. Do this for each IMAP account you have, and then after manually delete any previously stored drafts.