logging computer name

I am running Dovecot 2.3.21. One client has multiple computers in their LAN, connecting to my server with a static IP. One or several computers in that LAN keep logging in with failed password, but the Dovecot log only shows the public static IP, like this

Jun 25 10:39:20 server-name dovecot[689]: imap-login: Disconnected: Connection closed (auth failed, 2 attempts in 62 secs): user=xxxx@domainyyy.com, method=PLAIN, rip=client-public-IP, lip=server-IP, TLS, session=<MCLxoK4bksIO8zXR>

I tried to enable debug, but there is no more information about the LAN IP or computer names. Is there any setting which helps me with that purpose? So it will be much easier to locate the failed computers in that LAN?

Thank you.