Emails to distribution list being dropped

[dan-o365]

Emails have just been dropped with no NDR. These are internal users messaging an internal distribution group. The support tech had no idea, and refused to escalate the case. When I did a message trace this is the error I got

Drop Reason: [{LED=250 2.1.5 RESOLVER.GRP.Expanded; distribution list expanded};{MSG=};{FQDN=};{IP=};{LRT=}]

Is there a way to escalate cases? I've heard nothing in over a day even after requesting an update.

[#2]

That message is perfectly normal for emails sent to DLs, post the full message trace.

[#3]

@Vasil Michev 

Jun 4, 2019 4:00:22 PM

Receive

Message received by: DM5PR06MB2345 using TLS1.2 with AES256

Jun 4, 2019 4:00:22 PM

Submit

The message was submitted.

Jun 4, 2019 4:00:22 PM

Expand DL

The message was sent to a distribution list (DL) that was expanded to the recipients of the DL.

Jun 4, 2019 4:00:22 PM

Drop

Reason: [{LED=250 2.1.5 RESOLVER.GRP.Expanded; distribution list expanded};{MSG=};{FQDN=};{IP=};{LRT=}]

Jun 4, 2019 4:00:22 PM

Spam Diagnostics

 More information

Message ID:

<3FEF1E44-806D-4462-AA96-BC6329B700DC@****.com>

Message size:

48 KB

From IP:

50.243.147.228

To IP:

[#4]

You need the message trace details, Get-MessageTraceDetail. And you can also check the traces to the individual recipients, especially the ones that are having issues receiving messages.

[#5]

@Vasil Michev 

Where in office 365 am I allowed to use Exchange cmdlets?

[#6]

Nowhere, use PowerShell: https://docs.microsoft.com/en-us/powershell/exchange/exchange-online/connect-to-exchange-online-powe...