Or you can implement a policy server yourself. :)
The protocol is not complicated, json over http. See https://wiki.dovecot.org/Auth/Policy
-------- Original message --------
From: Aki Tuomi <aki.tuomi@dovecot.fi>
Date: 21/05/2018 19:13 (GMT+02:00)
To: Marc Perkel <marc@perkel.com>, dovecot@dovecot.org
Subject: Re: Dovecot blacklist?
https://github.com/PowerDNS/weakforced cn be used for this.
-------- Original message --------
From: Marc Perkel <marc@perkel.com>
Date: 21/05/2018 19:09 (GMT+02:00)
To: dovecot@dovecot.org
Subject: Dovecot blacklist?
lookup as a negative authentication so that if the IP is on a blacklist
then authentification fails even if they get the password right.
If this works I have a blacklist everyone can use.