Help troubleshooting a weird exchange SMTP error

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ANglEAUT

2307 posts

Uber Geek

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#2803190 29-Oct-2021 03:10

pomtom44: ... and no third party tools installed which are intercepting them (that im aware of at least) ...

For me 2 things spring to mind

database inconsistencies (which you would have seen in one of the many log files, so most likely n/a)
Anti Virus keeping a lock on a file somewhere - Microsoft Defender is still AV software installed on the machine. Make sure your exclusions are set correctly

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pomtom44

128 posts

Master Geek

#2803214 29-Oct-2021 07:28

ANglEAUT:

For me 2 things spring to mind

database inconsistencies (which you would have seen in one of the many log files, so most likely n/a)
Anti Virus keeping a lock on a file somewhere - Microsoft Defender is still AV software installed on the machine. Make sure your exclusions are set correctly

Ill have another look for database issues, there was a few errors which were showing up, but i didnt really look too much into them, as I was just scanning for SMTP errors
so could well ahve been a database error I overlooked

as for AV, both servers are configured with the same setup there, so unless the second one is storing files in a different place to the first, shouldnt be an issue

SirHumphreyAppleby

2838 posts

Uber Geek

#2803217 29-Oct-2021 07:34

pomtom44:

as for AV, both servers are configured with the same setup there, so unless the second one is storing files in a different place to the first, shouldnt be an issue

On access scanning should be off, but if the issue were file system related, a permissions issue would be more likely. I can't see any reason why Exchange would attempt to access a file immediately after it was written, so if an AV scanner were to cause issues, it's unlikely to be on e-mail submission.

pomtom44

128 posts

Master Geek

#2803286 29-Oct-2021 08:27

Okay, I managed to figure it out

Taking the comment about database issues, I did a deep dive into the logs (even non exchange related sections like the windows applications log) and found an error pop up when i tried to send an email
Turns out a previous developer (like 5+years ago) was working on a custom transport agent to parse emails and process them based on subject (essentially ticket tracking for our in house software) and was testing it on our secondary exchange server. but never got it fully working and just left a half finished project installed on the server

As it wasnt "exchange" which was failing, there was no error logs related to exchange, which is why it was just stopping
i found this transport role and removed it, and sure enough mail flows perfectly fine

so SirHumphrey was right with a transparent proxy, it was just within exchange, not before it

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