There are many other third-party tools available in the web market but only a few of them are reliable. I want to suggest you use the MacSonik AOL Backup Tool. It helps users to back up their AOL emails within a few steps. This AOL backup tool gives you the option to Remove Similar Emails in which you can remove duplicate emails from chosen AOL folders. Using this utility users can Filter AOL Mailboxes Emails where you can apply the mail filter option on it to backup the desired email only.