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Peter ChanFlag for Hong Kong

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Email issue (smtp)

Hi,
Is it certificate issue below? I remove certificate to 587 port of SMTP but issue persists.

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Craig Beck
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In order to determine exactly what is happening we would need to see a Wireshark trace from your server. It could be anything really.
The message indicates that the connection was terminated.
Without knowing the circumstance there could bevariations of issues.
Their firewall detects a signature of a virus like that terminates a connection.
Identifying exactly is difficult .

Are you sending an email with a large attachment?
Send this message to yourself as a test. If you get the message with this error it means that on the server there is a process that takes too long to acknowledge the acceptance of the message.

A certificate error occurs first, as the certificate is the first part of the connection establishment.
Easy answer is refer to logs on both end of transaction sending MTA + receiving MTA.

This will tell you the exact problem.

This type of message usually means the connection has simply been broken for some reason. Might be sending MTA or receiving MTA or some network segment between.

Tip: Before every trying to send, test your connection using SWAKS which will tell you if your port 587 submission is working.

SWAKS - Never leave home without it...

https://www.experts-exchange.com/questions/29215959/Cannot-send-emails-Linux-command-line-to-Google-SMTP.html provides details about SWAKS usage.
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ASKER

Hi all,
Regarding the relevant trace file, what is root issue of this? Why is it stopped/disallowed by the server?
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arnold
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SWAKS == easy

Wireshark == hard

Start with SWAKS first.

Post your entire SWAKS conversation.

Likely this will instantly surface the fix.