I'm running dovecot 2.3.18 under Debian 11.

I want to do something that's a bit unusual: when IMAP connections are attempted

from a few specific IP addresses, I want to force an IMAP authentication failure

from those connections, no matter what user ID and password are specified.

I know that I can use iptables to completely block imap access from those IP

addresses to the IMAP ports. However, in these specific cases, I'd prefer that

the connection goes through to dovecot, but for dovecot then to always generate

authentication failures for those specific connections ... even if a valid

user ID and password happen to be specified.

Is there a way to do this in dovecot?

Thank you very much in advance.