If re-add an email will it replace existing data?

You have several options when dealing with duplicate data. When you create a new list, you can select how you want the Contact Management tool to process duplicate data that gets uploaded. This function is called "Merge Options."

The point of the merge options is to resolve conflicts when a contact that is being uploaded onto a new list already has a contact profile in our system. By merging new and existing contact data, you can continue adding to individual contact profiles to make them more complete, for more targeted marketing. In this way, you don't have multiple profiles for the same person, which is inefficient and could become very confusing. The merge columns that are selected in the "Merge contacts that share" drop-down menus are the columns that decide where a conflict exists.

For example, let's say we have an existing contact profile in the system:

[email, first name, last name, phone]

bob.smith@example.com, Bob, , 15555555555

And the uploaded list has a new contact on it with:

[email, first name, last name, phone]

bob.smith@example.com, , Smith, 12224441234

If you select the merge field as "Email" (the default), then you have a conflict (the new contact matches an already existing contact) and you will need to merge the new uploaded contact into the existing contact profile, because the email addresses are the same.

If you chose to merge based on "Phone," then there would not be a match and the system would not merge the existing contact and the new contact together. A new contact profile would be created and that email address would appear twice on two different profiles because the phone number is different.