On Tue, Sep 01, 2020 at 05:22:30PM -0400, Wietse Venema wrote:
> > FWIW, the following is not explained as clearly in the Postfix
> > documentation as one might wish, and it would be good to have better
> > coverage of this topic in the docs (in the appropriate places):
> >
> > - What is a delivery agent?
> > - How are they related to transports?
> > - Which Postfix components are delivery agents?
> >
> > - What is an internal service (that is not a delivery agent)?
> > - What are the various internal services?
> >
> > - What are the "..._service" parameters, and in what context
> > can they be used (correctly)?
> >
> > Some of this is in http://www.postfix.org/OVERVIEW.html, but the
> > taxonomy of internal services is not explicitly presented.
>
> OVERVIEW.html would be the right place for such information; it is
> the only document that shows each component in context, and it would
> not make sense to have the taxonomy separate from the overview.
>
> There is no good reason to cover detail of services that are not
> already covered in configuration examples.
>
> In particular, internal services do not feature in Postfix configuration
> examples, such as bounce, anvil, dnsblog, and trivial-rewrite. This
> is for a reason. The only sensible guidance for these is to leave
> them alone or risk breaking Postfix.
We're pretty much on the same page here, but I do see users from time to
time thinking that all the various services are interchangeable and that
one could use bounce(8) as a delivery agent, or discard as a bounce(8)
service, ...
It would be nice to have some text that briefly draws a distinction
between the delivery agents:
- smtp, lmtp
- local
- virtual
- pipe
- discard
- error, retry
and all the other (internal services) that users cannot repurpose for
some other task, as though they're delivery agents.
--
Viktor.
