Try getting more verbose logs using dovecot's logging mechanisms.
auth_verbose=yes
auth_debug=yes
It seems that you aren't authenticating your master users against your
passwd file, instead you are authenticating against your OpenDirectory.
- [Dovecot] Can't get authentication for masterusers on Mac ... Gilles Celli
- Re: [Dovecot] Can't get authentication for masteruser... list
- Re: [Dovecot] Can't get authentication for master... Gilles Celli
- Re: [Dovecot] Can't get authentication for ma... list
- Re: [Dovecot] Can't get authentication fo... Gilles Celli
- Re: [Dovecot] Can't get authentication for masteruser... Giuseppe Chiesa
