spam folder and POP users

I am new to actually running dovecot. I actually still use POP as I have for YEARS and thunderbird does not make it easy to convert to IMAP...

My server is moving all tagged spam into the IMAP spam folder. Very nice for the IMAP users, but not for the POP users. Of course the server don't know, and the mysql database for users does not have any flags for this. Don't want my server to fill up with spam from POP users that don't know to check via IMAP.

I am using roundcubemail for the webmail IMAP client. Is there any way for POP users to indicate that they do not want spam so nicely auto moved to the IMAP spam folder?