2FA/MFA with IMAP & postfix/submission

[Alex]

Hi, I have a dovecot-2.3.13 system on fedora34 with a few hundred
IMAP4 accounts, as well as postfix users using submission. Clients are
using primarily Outlook on Windows and old squirrelmail.

Are there multi-factor options available?

If it is not available, do you have any recommendations on where I
should look to do this?

All of the links related to this topic appear to be very old, or
limited to Linux PAM users.