Bug#315128: /etc/mailname clarfication

[Florian Weimer]

* Manoj Srivastava:

>  Umm, policy states:
> --------------------------------------------------------------------------
> 11.6. Mail transport, delivery and user agents
> ----------------------------------------------
>
>      ...
>
>      If your package needs to know what hostname to use on (for example)
>      outgoing news and mail messages which are generated locally, you
>      should use the file `/etc/mailname'.  It will contain the portion
>      after the username and `@' (at) sign for email addresses of users on
>      the machine (followed by a newline).
>
> --------------------------------------------------------------------------
>
>         Seems pretty unambiguous to me, but then, I am biased ;-).

It's confusing because it refers to "hostname" instead of "domain".
In the context of RFC 2821, "host name" refers to the argument of the
EHLO command or Received: header lines.

For typical end users, the host name differs from the domain name, the
EHLO argument has to be chosen dynamically for remote deliveries, and
it's sometimes impossible to use a proper host name in Received:
headers (because it's generated when the host is offline, and it's not
possible to obtain a unique hostname/time pair).