[Pkg-exim4-users] HELO and 192.168

[Ross Boylan]

On Sat, Oct 08, 2005 at 06:23:40PM -0400, Jeff Abrahamson wrote:
> My workstation, astra, 192.168.0.7, is (correctly) not visible via
> global DNS.  It sends mail and rewrites headers just fine (see above
> headers, e.g.), but some machines check resolution of the address that
> exim4 provides on the HELO line.
> 
>     HELO astra.purple.com
> 
> I've been googling and reading docs for some hours to figure out what
> to do, but no luck.  Any suggestions?  (This is debian sarge, exim4
> version 4.52-2.)

I've been experiencing a very similar problem.  A number of sites try
to verify the envelope sender of the message; I have a suspicion that
some also try to verify the machine doing the sending.

I'm uncertain what checks one runs into in practice; the main one that
has caught me is the check of the domain of the envelope sender.  I'm
not sure if that's via MX (which would make sense), or general DNS.

In principle, a system might attempt to callback to verify the sender,
or do some checks on the host machine.

For those reasons, I've switched to a satellite configuration (one of
the Debian options settable in dpkg-reconfigure exim4-config or
/etc/exim4/update-exim4.conf.conf) and hiding my system's name.  I
found the Debian defaults didn't rewrite as extensively as I needed
(cc and bcc were left untouched) so I did it manually.  (I posted some
queries about that a few days ago, because I'm fuzzy on the details
and am still hoping someone will elaborate).

You can rewrite using exim's general facilities, but I've chosen
transport level rewriting so it only affects outgoing mail.  In
particular, see the return_path option for transports to change the
envelope sender.  Note it is *not* a rewrite rule (I found that out
the hard way); it is a regular expansion which you should set to the
value you want.

Ross Boylan