How does Dedupe Subscriber resolve the duplicates among email ids used in marketing cloud?

Hi Pranav,

It de-dupes by Email Address, not Subscriber Key. So if you have the same email address with multiple Subscriber Keys, it'll pick one and skip the others.

There are also AppExchange applications that may help you. You can go to http://appexchange.salesforce.com/ and search for duplicate email or dedupe or de-dupe or other search terms to find apps that may assist you with preventing duplicate records.

Hoping this will help you:

Thanks.