Hello!

The following patches provide a mean to specify a user and group for a
setuid program, and uses that to fix a setgid permission issue in the
context of the opensmtpd service.

Christopher, you should be able to leverage this new facility to
configure the uid/gid of the sendmail program to that of the smtpq user,
like this:

--8<---------------cut here---------------start------------->8---
(operating-system)
  [...]
  (setuid-programs (cons (list (file-append sendmail "/usr/sbin/sendmail") "smtpq")
                           %setuid-programs))
--8<---------------cut here---------------end--------------->8---

The smtpq user is created as part of the OpenSMTPD service definition.

Thank you,