PMDF User's Guide
OpenVMS Edition

With the VMS MAIL mailbox, after a message is read (retrieved) by a POP client, it is marked as read and normally will be moved to the MAIL folder when the session terminates. (Your system administrators might have chosen to configure the PMDF POP server to have a different behavior.)

If a VMS MAIL message is deleted by the POP client, the message is marked for delete and moved to the WASTEBASKET folder when the connection is closed or the client exits. If you have enabled AUTO_PURGE in your VMS MAIL profile, then all messages in the WASTEBASKET folder will be purged when the connection is closed or the client exits. If you have not enabled AUTO_PURGE, then the deleted messages stay in the WASTEBASKET folder. There is no way in POP3 to set AUTO_PURGE; it has to be done in VMS MAIL or PMDF MAIL.