Preventing VAX running VMS / Multinet from being used as SMTP relay

Peter Coghlan cctalk at
Thu Nov 30 17:28:13 CST 2017

> I have a microvax set up with VMS 5, running MULTINET (and decnet
> locally).   The server has a FQDN and after a while being exposed to the
> WWW someone out there started using the server as an SMTP relay.  I can
> disable and clear the queue, but I'd like to block entirely this from
> happening in the first place.  I'd like to learn more about how this
> happens in VMS.
> Anyone have had this same problem before?  I realize back when VMS 5 was
> current it was not so much of an issue, but today it is.  I am working on a
> solution.  I can envision a few ways including blocking the smtp relay port
> from the firewall, but if possible I'd like to set up a VMS Multinet
> solution as a learning exercise.

I had this problem about 25 years ago.  I suspect lots of people did.

In the VMS world, networking stacks are separately packaged from the base
operating system and it is possible to install one or more of DECnet, TCP/IP,
X25 and various other networking products and have them all running

VMS doesn't know or care about SMTP, the issue here is with Multinet which
seems to be what was installed to provide TCP/IP networking on your machine.
Multinet includes a basic SMTP server which can be used to move mail between
VMS MAIL and the internet.  Very old versions of Multinet came with SMTP
relaying enabled because this is what the standards required at the time.
Later versions came with easy ways to disable SMTP relaying.  Later still
versions shipped with SMTP relaying disabled out of the box when spammers
targetting open relays became a serious problem.  More recently still,
Multinet comes with pretty much all of the TCP/IP servers it provides disabled
and requires the installer to enable the services they want, leaving less
opportunity for surprises when servers are running that nobody knew existed,
except the bad guys targetting them.

The Multinet SMTP server is pretty basic and people who are serious about
doing SMTP on VMS typically disable it and install a proper mailserver like
PMDF.  That's my excuse for not knowing how to disable SMTP relaying in
Multinet.  That and because it probably varies for different versions of
Multinet and you haven't said what version of Multinet you have.  I used to
be one of the people supporting Multinet in this part of the world and I
seem to have inherited a stack of Multinet documentation for different old
versions so if I knew what version, I could probably look it up.  I think the
documentation for the most recent couple of Multinet versions is on the
Multinet website:

Try the Adminstrator's guide or Adminstrator's reference.

I do however know how to disable the SMTP server in Multinet completely:

Configuration modified, do you want to save it first ? [YES]

Peter Coghlan

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