Dovecot and multi-factor auth support

OpenBSD 6.6 amd64
OpenSMTPD 6.6.0
Dovecot 2.3.9.3 (9f41b88fa)
login_duo 1.11.2

I'm working with an OpenSMTPD/Dovecot installation that will support
users authenticating over the internet and I'm curious if any form of
multi-factor authentication is possible for IMAP (and optionally,
SMTP).

Currently SMTP auth and Dovecot both authenticate users over TLS using
their system user passwords. I have also set up Duo MFA for sshd using
the login_duo package so admins can additionally authenticate with a
push notification to phone.

Is there any sort of supported way of wiring up login_duo with
OpenSMTPD and Dovecot, or using bsdauth in some way to enforce a
second auth factor?

--
Darren Spruell
phatbuckett@gmail.com