Where does "Downstream server error" come from?

Bryan Tong contact at nullivex.com
Mon Jan 20 01:09:56 UTC 2014

I was thinking that maybe the rogue host configured on the IP didn't have
any mail software installed and it was just a random service returning the
error message as it didn't know how to handle the request.

On Sunday, January 19, 2014, Brielle Bruns <bruns at 2mbit.com> wrote:

> On 1/19/14, 5:32 PM, Scott Howard wrote:
>> I've come across this error (or something very similar to it) before.  I
>> can't remember the exact product, but it turned out to be a transparent
>> SMTP proxy somewhere in the path - possibly on a UTM firewall, but I could
>> be wrong about that part...
>> Not overly helpful I know, but might point you in the right direction...
> Almost sounds like one of those annoying consumer Antivirus programs with
> the smtp/imap/pop3 proxies that wedge themselves in between mail client
> connections.
> Trying to remember what the error it was giving the other day on the
> machine I worked on, when the proxy itself had been blocked by the local
> system's firewall...
> I'd have been curious if you got the same error message trying to go out
> on 587 instead of 25.
> Thinking about it, that error screams of something like what a
> multi-server Exchange setup would say if something went wrong on the
> backend.
> Not entirely helpful either, but...  never know.
> --
> Brielle Bruns
> The Summit Open Source Development Group
> http://www.sosdg.org    /     http://www.ahbl.org

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