If anyone can help

My outlook account on my computer keeps bringing back old emails over and over. Often over 500 old emails that were long deleted up to 3 years ago are brought back into my inbox. I have no idea what to do.

My outlook account does have 2 accounts pulling into it, and i did read that there is a problem with this;

Diane Poremsky posted this comment to this problem previously in 2012;

Outlook 2010, due to changes in how the "message manager" is handled, may download messages over and over if you deliver multiple accounts to one pst file. To fix, create a separate pst file for each account. In file, account settings, select the account then Change folder button to change the delivery location to a new pst. 

I however work on a Mac and for the life of me cannot figure out how to change these settings. It clearly doesn't work the same as she explained. 

CAN ANYONE PLEASE HELP???

Jared