Mail (Mountain Lion): If you receive a message more than once
There can be several reasons why you receive a message more than once.
- You may be listed twice on the sender’s individual or group list.
- You may have created rules that are causing messages to be duplicated. Choose Mail > Preferences, click Rules, and then verify them.
To find a problem rule, turn off all rules and then turn them back on one at a time until the problem recurs. Also look for rules whose actions move or copy messages to the Inbox or to a custom mailbox located in the Inbox. These actions create a loop, so that each time a message is received in your Inbox, the rule is run and the message is moved or copied to the Inbox again. Edit the rule to move or copy messages to a mailbox outside of the Inbox.
- You may be using a Post Office Protocol (POP) account in Mail on different versions of OS X. Use the account in Mail on only the most recent version of OS X.
By default, Mail doesn’t show duplicate messages. To know when you receive duplicates, choose Mail > Preferences, click Viewing, and then choose Custom from the “Show header detail” pop-up menu. Now when you receive duplicates of a message, a Duplicates link is included in the header details of the message. Click the link to see the duplicates.