dovecot - Mar 2021 - Can Dovecot honor Outlook's "leave mail on server for X days" setting?

I googled around for a quite bit but surprisingly came up empty for an
answer to this question which I'm sure has been broached before.

I've got a linux box running dovecot/postfix using maildir format. I
was surprised to learn that a client that had many GBs of email was
running POP3, not IMAP. It turns out they had a setting to delete POP3
mail after X days turned on but it just went ignored.

I know this is not how POP3 is supposed to work, but is there a way to
get dovecot to honor the user's settings in Outlook? Or should I just
tell the client to turn this off and use a proper IMAP account?

On Tue, 2 Mar 2021, Steve Dondley wrote:
> I've got a linux box running dovecot/postfix using maildir format. I
> was surprised to learn that a client that had many GBs of email was
> running POP3, not IMAP. It turns out they had a setting to delete POP3
> mail after X days turned on but it just went ignored.
>
> I know this is not how POP3 is supposed to work, but is there a way to
> get dovecot to honor the user's settings in Outlook? Or should I just
> tell the client to turn this off and use a proper IMAP account?
It's not dovecot (or any POP3) server's job to implement this setting,
it's
the client's.  Typically, the mail reader downloads a list of messages,
then issues "DELE" commands to remove messages based on whatever
criteria
the user had set.  Dovecot has no idea what the user's setting is.

Other people seem to have the same problem:

 	https://www.hmailserver.com/forum/viewtopic.php?t=29988
 
https://answers.microsoft.com/en-us/msoffice/forum/msoffice_outlook-mso_other-mso_2010/outlook-2010-not-removing-email-from-pop3-server/f952f469-a95b-4a5a-a805-a304354c2c1a
 
https://portal.smartertools.com/community/a90038/outlook-pop-leave-mail-on-server-for-days-not-deleting-mail.aspx

You may have to create a POP3 session log to diagnose what POP3 commands
you're client is issuing.

Joseph Tam <jtam.home at gmail.com>