I've been trying to get Dovecot working in Debian 12 with LMTP and I have noted:
- Webmin does not install dovecot-lmtpd
- Even with it installed, it cannot be enabled. It looks like lmtp needs to be added to the protocols line in /etc/dovedot.conf to enable it. Teh menu option exists in Dovecot > Networking and Protocols, but it does not work.
- There doesn't seem to be a way of setting up the LMTP Unix socket in Dovecot, but it can be set up in Postfix
- You have to set "auth_username_format = %Ln" in /etc/dovecot/conf.d/10-auth.conf to enable mail delivery to strip the "@domain" part from the email address to get the username.
This is new to me - what does LMTP do for you?