Question/Topic: How to find email list duplicate records?
On the 
Advanced menu, click 
Maintenance.
In the 
Database Maintenance window click 
Duplicates.
Select a field in the 
Select Duplication Field box. (this field will be checked for duplicates).
If you want to only view the duplicate records click on 
Display Duplicate Records  button. 
If you want to eliminate the duplicate records click on 
Delete Duplicate Records  - Keep First Record button. This function will delete all duplicates (the first record will be kept). 
WARNING: This operation cannot be undone. 
If you want to display all email list records afterwards right click on the small 
Filter Button at the top of the left panel (which says 
Normal Filter) and select 
All Records.