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S SlomoFlag for United States of America asked on

SMTP server not relaying some mail to Office 365 mailboxes

We have an IIS 6 SMTP server that is relaying messages from applications and devices to our users on an Office 365 tenant. Recently, users have not been receiving certain messages that were generated by our ERM system using the smtp relay.  The procedures on the ERM server logs report as completed  successfully but the smtp server logs do not seem to show these entries.  There are a number of messages that do go through and they do show up in the SMTP log files. Are there restrictions in the SMTP virtual server that would drop the connection but not show up in the logs? Also on the Office 365 end, are there any logs that would show a failed connection from this connector? The connector is set up with the conditions that is must come from the specified IP and the sender email address is from an accepted domain. Any help would be appreciated.

Microsoft OfficeMicrosoft 365Chat / IM* IIS SMTP Server

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S Slomo

8/22/2022 - Mon

Did you check the logs in O365?
Is there any recent changes in your ERM system?
S Slomo

Besides Message Trace in Office 365, is there somewhere else I can look for a log of events for the relay connector-like if an email was dropped because of too many recipients, or reaching a rate limit? If looked through Message trace and do not see the messages that we were expecting from the system.  The configuration of the ERM system has not changed. New workflows that generate emails are created pretty regularly.  
David Favor

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S Slomo

The problem turned out not to be an email relay problem, as these messages did not show up in the relay logs. There was a stored procedure in the SQL database of the ERM system that was not updating a field and so the criteria was not met for sending out the emails. Once this was resolved, the emails went out as scheduled. The next problem is that the SQL database ldf file is growing and doesn't appear to let me shrink it, but that's a problem for another forum.
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