If you're receiving a message that says this email has already been entered into the system, you can go into Contact Management and search to find where this email address is located. Make sure to locate the search field and select email from the drop-down menu.
Note: You may not be able to find the contact with the same email address if you search by Contact Name. If you have the same contact added but their name is misspelled, they will not appear in your search results.
When searching by email, you don't have to type in the full email address. The first few letters of the email address will allow you to find the email through your list of contacts. Once found you can merge the two Contacts to make sure that all necessary information isn't lost by deleting one of their records.