Return Receipt sent in error

Wonder if anyone has seen this before or any other problems using return receipt with the web client?

User sent mail from web client (6.0.1 from 2000 wkst-- server is on W2000, Domino 6.0.1 a well) with return receipt to two users on our notes domain.

When one of the recipients opened the mail a return receipt was sent to everyone on one of our Notes email groups (that included many external addresses). The group was not listed in the email. (This did not happen with the second recipient a return receipt was sent only to the sender)

The ‘from’ feild when viewed in the recipients mail was blank, but showed a “sent by:” with the correct senders info as if he was accessing the wrong database. When looking at the ‘Inbox’ view just had this character ’ □ ’

The email is in the sent folder when looking on senders mail DB. When we opened the mail from senders DB it was again sent to all members in that group.

A virus scan found nothing (on either senders or recipients machine).