okay, I'm getting a little further now. Exim -bv fails because no_verify is
set in the userforward router.
No_verify is set because exim doesn't have the required privileges to read
the file as user mail. Turning on verify generates the "unable to set gid
or uid" error. So verify still fails.
I'm not really concerned that a-validsuffix@??? is valid. I'm only
concerned that a@??? is valid at the smtp rcpt to: phase.
I guess this means creating a verify only router. But I'm stumped as to
where to go to next.