Okay,
Let's try this a different way.
I've been able to configure past dovecot to have a different mail_location setting for the same user, but with different protocols.
When the user requests POP3S, I adjusted the mail_location to /var/mail/$USER (with mbox in use).
When that *same* user requested IMAPS protocol, the required mail_location is the Maildir folder.
This allows for independent two mail storage locations, one for the use of mbox and the other for the use of Maildir *and* for the same user.
Some users only require mbox with others only requiring Maildir.
So, I need to cater for each of these situations.
How might I adjust current dovecot configuration to provide different mail_location settings for different protocols?
Old dovecot allowed me to run a script before POP3S processing that gave me the chance to adjust the mail_location variable. That is what I need now, just for POP3S.
Thanks AndrewM