2.4.0 on MacOS

I got bitten by the upgrade from 2.3 to 2.4 on my MacOS laptop. I know enough to be dangerous here and had a set-up that was working fine, but now I can't quite figure out how to modify my conf file to work correctly.

The current error I'm getting is that there is no group "dovecot" even though I've created one and made the default user a member:

Fatal: service(dict) Group doesn't exist: dovecot

More broadly I find the documentation hard to follow, as others seem to have noted in the past.

Any help appreciated.

Jackie