Why would unique email addresses display in the System Smart List: Possible Duplicates? The only filter on the smart list is "Duplicate Field IS Email Address" and these emails only have one record per email.
Do you happen to have multiple partitions/workspaces? If there are 2 records with the same email address, it will show as a possible duplicate, but you will only see 1 of the records in a partition if that is all it has access to.
Hi Jackie Potts, that's a good thought! However, I just checked my 2nd workspace and the same single record shows for each email (same Marketo ID).