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@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.
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