Email: Could not mail <mail server>

[jwckauman]

Our Symmetra 40K has a "UPS Network Management Card 2" in it and it is configured to send us email whenever a certain condition occurs (e.g. on battery, self-test).  We have an on-prem Exchange Server 2016 (latest CU), with a SMTP relay that doesn't require authentication or encryption (the UPS is allowed to relay because we told the mail server to allow all SMTP traffic from the UPS Network Card IP Address).  In the past, I used the DNS name for the mail server, but recently changed it to the IP address instead to rule out DNS.  At some point, we started noticing we weren't getting all the emails we were expecting.  For example, we had a power blip this AM that resulted in the UPS sending us an email about the device going on battery.  When the blip ended, we expected to see a 2nd email stating that the UPS was no longer on battery, but we never got the 2nd email.  When i checked our logs, I see several of these system events. 

07/28/2021

12:57:05

System

Email: Could not mail '10.0.0.70'.

When I try to generate test emails, i also get some of them and others fail with the message above in the event log.  I have tested both user and distribution group email addresses (no different between the two), and also ruled out alert types (doesn't matter what the alert is, or if i use test alerts).  Time of day doesn't matter either.   

1. Is this a known issue with the UPS NMC 2 models?  are they still supported?  do i have the latest firmware?  we are running v6.9.6.

2. this is a Symmetra 40k "3-phase" unit.  Can i upgrade to the UPS NMC 3 model?  or any other card options that are newer and still getting firmware updates?

3. any ideas for troubleshooting?  I don't see failures in the SMTP receive logs on the mail server.  but i may not be looking in all possible locations?

Any help you can provide would be much appreciated!