Q&A: Mail duplicated

Q My iMac is connected to the Internet via cable. I use Apple’s Mail to read and send email, through my ISP account, but each incoming message arrives in duplicate, and no matter how I try to delete them, they keep returning in a mailbox named ALL MAIL. How can I restore normal service?

A Assuming that you normally use POP and not IMAP to collect your mail, this is most probably because of a misconfiguration in Mail’s settings. A few ISPs may still default to leaving email on their server even when you access it using POP. Normally, that would only happen if you used the other means of collecting email, IMAP. You should check this out in your ISP’s online help information, focussing particularly on the recommended configuration of mail clients. Most ISPs now provide detailed instructions for setting up an account in Mail.


Open the Mail application and use its Settings command in the Mail menu to show the preferences dialog. Click on the Accounts tool, then select your account in the left of the window. Select the Advanced tab. Ensure that the top three options are ticked, in particular the third, which refers to removing copies from the server after retrieving a message. Save your new settings, and try them out. Initially you might find the ‘Remove now’ button in that view a help in getting rid of all your old email.

Updated from the original, which was first published in MacUser volume 27 issue 13, 2011.