[InterNetNews/inn] 8e6120: Document news gatewaying to mail in mailpost

[Julien ÉLIE]

  Branch: refs/heads/main
  Home:   https://github.com/InterNetNews/inn
  Commit: 8e6120b857950f197170c28732415686058d8891
      https://github.com/InterNetNews/inn/commit/8e6120b857950f197170c28732415686058d8891
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2022-02-04 (Fri, 04 Feb 2022)

  Changed paths:
    M frontends/mailpost.in

  Log Message:
  -----------
  Document news gatewaying to mail in mailpost

How to set it up was not clear at all.  Now document how to set up
approvals (-a flag and A access in readers.conf) and moderation
(in moderators).

Use a better name for the persistent database directory in the
example (/var/tmp was not a good choice).

Mention in -b and -t that mailpost is as often as not run as the
mail user.

Mention which inn.conf parameters are used for the domain name.

Mention that the -a argument is usually an e-mail address.