I HAVE RANG FOUR DIFFERENT COUNTRIES AND STILL NOONE IS ABLE TO HELP ME!

I NEED TO STOP MY OUTLOOK ON AN IMAC FROM DOWNLOADING ALL MY EMAILS AGAIN AND AGAIN. I HAVE FOLLOWED ALL THE HELP TIPS THAT ARE ON DIFFERENT FORUMS BUT STILL NOTHING IS WORKING - I AM USING A POP EMAIL ACCOUNT AND IT IS CONNECTED TO A SERVER THAT CONNECTS ALL OF MY OTHER COMPUTERS! I HAVE 2 COMPUTERS OUT OF 10 THAT ARE DOWNLOADING AGAIN AND AGAIN AND NOW I HAVE THOUSANDS OF EMAILS IN MY OUTLOOK AND I AM UNABLE TO STOP THEM!

PLEASE HELP.
THANKS