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

Camiel Vanderhoeven camiel.vanderhoeven at
Sat Dec 2 03:33:45 CST 2017

On 11/30/17, 9:26 PM, "cctech on behalf of william degnan via cctech"
<cctech-bounces at on behalf of cctech at> wrote:

>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
>solution.  I can envision a few ways including blocking the smtp relay
>from the firewall, but if possible I'd like to set up a VMS Multinet
>solution as a learning exercise.
>I am open to suggestions, and once I find the solution I'll post it.
>I understand that this kind of thing is not cookie cutter, there are
>different levels one could address something like this.  I have a comcast
>business router, and one of the 5 IPs I have is NAT assigned to the
>internal 10.1.10 port of the microvax.
>This is the same machine I wrote about previously as with then, thanks for
>your help.  I find the best way to learn is on the actual hardware warts
>and all.

Look at the SMTP_SERVER_REJECT file example here:
It¹s a set of rules that decide whether a message gets rejected (rule
ending in ³y²) or let through (rule ending in ³n²). You¹d normally set
this up to first let through those emails you want, then reject everything
else at the end of the rules file.

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