off list person name protected =================== Sorry no. That is what you would think. But there are many types of data structures that can duplicate keys. Only if it an indexed file can you have only one key. PS I first touched a computer in 1969 -----Original Message----- Paul, I'll let others address this publicly. But my guess is that the email address is a key field in the database structure used by Mailman, in which case it would not be possible to have two separate records for the same key field; that should produce an error message. -- That is what you would think. But there are many types of data structures that can duplicate keys. Only if it an indexed file can you have only one key. PS I first touched a computer in 1969 -----Original Message----- Paul, I'll let others address this publicly. But my guess is that the email address is a key field in the database structure used by Mailman, in which case it would not be possible to have two separate records for the same key field; that should produce an error message. --