De-duplicate by Email Address

I have a list that I need to make an email blast. When I performed a lookup with the database based on email address field I found there are few duplicates for few contacts, meaning the same contact exists in the database more than once. Will need to make an email blast by tomorrow so hoping for a quick solution here. What do you think might be the best approach:

1. Merging those duplicate contacts

2. Adding the logic within the smart campaign so that system won't send email more than once to the same contact.

I am not sure about how to implement this but this was on top of my head.