Different realm for different listeners?

[Chris Adams]

I see this has been asked a few times over the years (but not in several
years), and the response was along the lines of "maybe someday", so I
figured I'd see if someday was here yet...

I have a need to have a different default realm for different listeners.
Basically, I've a bunch of different domains, and a few of them insist
their users not be required to authenticate with "user at domain" and just
use "user", and I'm trying to make this work without separate daemons
and/or VMs.

I'll be using Dovecot 2.2 (most likely 2.2.10 as provided by RHEL/CentOS
7).

Thanks.  If there's not a way to do this directly in Dovecot, does
anybody have any suggestion that doesn't require several different VMs?
-- 
Chris Adams <cma at cmadams.net>