How to remove duplicate emails on outlook?

I was using outlook connector before, but now simply configure the settings manually.
But after this change, outlook starts downloading all my mails in duplicates. I am currently using Blackberry for the same email address, and also sometimes I use my Ipod Touch to check mails.
I have tried downloading the add-ins to remove duplicate emails, but I can only go until step 2.
Now, all my mails are downloaded 3 times.
Please help.