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smtp email NAV 2016 fails sending intermittently

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Posted on by Don Saito

We're facing an odd issue where emails sent from NAV will not send intermittently. The error is:

/The SMTP mail system returned the following error: /Failure sending email/. Authentication failed because the remote party has closed the transport stream./

The email account is an O365 account. This issue started happening after switching from on-prem exchange to O365.

Any ideas?

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Don Saito 7 on at

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smtp email NAV 2016 fails sending intermittently

Thank you Yun, it appears those settings are only in Business Central, not NAV 2016.
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YUN ZHU 74,115 Super User 2024 Season 2 on at

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smtp email NAV 2016 fails sending intermittently

Hi, you can check the settings below.

https://learn.microsoft.com/en-us/dynamics365/business-central/dev-itpro/administration/configure-server-instance#Compatibility

Hope this helps.

Thanks.

ZHU
Don Saito 7 on at

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smtp email NAV 2016 fails sending intermittently

Yes, I agree it looks like a TLS version issue, though I'm not sure how to remedy that from the NAV development side.
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YUN ZHU 74,115 Super User 2024 Season 2 on at

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smtp email NAV 2016 fails sending intermittently

Hi, I'm not sure because you also had times where the send was successful, but it looks like an O365 SMTP TLS version issue.
Hopefully other experts can give you better advice.

https://community.spiceworks.com/topic/2334614-o365-smtp-tls-1-0-is-it-my-watchguard-firewall

Hope this can give you some hints.

Thanks.
ZHU