configuring dns/sendmail for two different servers

[Gregory Shapiro]

> Maybe I misread but both of those features (I have used the second but  
> not the first) seem to be all or nothing forwarders (i.e. xxx at domain is  
> forwarded for all xxx not just some xxx)

LUSER_RELAY is only for unknown users.  If you user virtusertable,
you'll need to list out all valid users and then add a catchall @domain
map entry.