Set-ExternalInOutlook - Keeps reverting to False

Question

Hello- We have an odd issue: We are attempting to configure the in-line "External" tag using the supplied functionality in 365 via powershell: (Set-externalinoutlook)

We've done this one several clients without any issue - it can take a few days to fully update on all the users Outlook clients but it works well and doesnt' change the message like mailflow rules.

So the problem is - it's automatically turning itself off after about 2 hours or so and we cannot figure out why. None of the enterprise apps or any other users are making the change disable, and there doesn't appear to be anything in the audit logs that is causing it. We have tried other accounts with permissions, Global admins, and so on. Yet every single time it reverts. Even Microsoft support, which I have been working with for TWO MONTHS now has no clue as to why it is happening and is still examining a Fiddler trace(for who knows what reason) to troubleshoot further. They gave me this script to test, and you can see below how it does set the value to $true, and after a period of time it just goes to $false.

Anyone have any ideas? Script follows below:

PS C:\windows\system32> write "Set-ExternalInOutlook"; $((get-date).ToUniversalTime()); Set-ExternalInOutlook -enabled $True; 1..40 | % {Start-Sleep -Seconds 900; write "Get-ExternalInOutlook ; Count $_ "; $((get-date).ToUniversalTime());  $res = Get-ExternalInOutlook; $res.Enabled ; if ($res.Enabled -eq $False){  write "the value was reverted"; break; } }
Set-ExternalInOutlook

Monday, April 29, 2024 9:23:06 PM
Get-ExternalInOutlook ; Count 1
Monday, April 29, 2024 9:38:08 PM
True
REDACTED TO FIT THE MESSAGE
True
Get-ExternalInOutlook ; Count 6
Monday, April 29, 2024 10:53:26 PM
True
Get-ExternalInOutlook ; Count 7
Monday, April 29, 2024 11:08:30 PM
True
Get-ExternalInOutlook ; Count 8
Monday, April 29, 2024 11:23:31 PM
True
Get-ExternalInOutlook ; Count 9
Monday, April 29, 2024 11:38:38 PM
False
the value was reverted

Answer 1

1. The answer was what we thought the issue was all along. Blackpoint, our MDR, had created the "Set-ExternalInOutlook" as a configuration item in their UI. Their first support call did not acknowledge this, they only told me that the issue wasn't on their end.

2. Microsoft was also at fault. They took 2 months to be able to properly audit the issue in logs and tell me where I could determine what was resetting the configuration.

All has been resolved with vendor by enabling the configuration so their App registration doesn't see that it's on and revert to the setting in their portal.

Thanks.