Yes, you can add the contact even if their email is already present in the system.

There are few things to note regarding assigning contacts to a campaign:
  • Contacts can be assigned to a campaign by another associate if they have not opted into the campaign within 20 days of being sent the opt-in email.  After 20 days of no activity from the contact, they can be assigned to a campaign by another associate. 
  • For Example: 
    • User A adds Contact X to their Prospect by LegalShield account and assigns a campaign.
    • Contact X doesn’t opt-in within 20 days of the opt-in email being sent. It becomes possible for another User to assign Contact X to a campaign.
    • User B adds Contact X to their account and assigns X to the campaign. Then Contact X will show as Released for User A and will have a Gray status dot.
    • User A can still send resources to Contact X directly but cannot add them to a campaign.