Message to 365 group is dropped

Question

Hi all,

I'm using Exchange online hybrid mode.

From ECP , I create a Microsoft 365 group, allow external sender sending to this group, not create team for this group.

When external or internal sender send mail to this group , it's drop , logs as below

Subject: test

Sender: ******@contoso.com
Recipient: ******@contoso1.com Received -> Processed -> Delivered

Status: The message was delivered to the recipient's Inbox folder.<br/><br/><b>Delivery time:</b> ‎12/29/2023 4:21:37 AM (UTC)‎

More information: <div>If the recipient can't find the message in their Inbox folder, it might have been deleted or moved to another folder (such as Junk Email) either manually or automatically based on an Inbox rule or Sweep rule the recipient set up. Ask them to search for the message across all folders in their mailbox.<br/><br/><b>Tip:</b> If the recipient still can't find the message in Outlook, they might be having connectivity issues. Ask them to try restarting Outlook or use <a href='https://outlook.office365.com/owa/' target='_blank'>Outlook on the web</a> to check for the message. To see detailed steps for fixing Outlook, see <a href='http://go.microsoft.com/fwlink/p/?LinkId=708526' target='_blank'>Fix Outlook connection problems in Office 365</a>.</div>

Date (UTC) | Event | Detail |

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12/29/2023, 11:21 AM | Receive | Message received by: PSAPR06MB4295.apcprd06.prod.outlook.com

12/29/2023, 11:21 AM | Submit | The message was submitted.

12/29/2023, 11:21 AM | Expand DL | The message was sent to a distribution list (DL) that was expanded to the recipients of the DL.

12/29/2023, 11:21 AM | Transport rule | Transport rule: 'Set disclamer for internal message', ID: ('2363B4A5-F500-42C7-A606-8EC47AA269FA'), DLP policy: '', ID: (00000000-0000-0000-0000-000000000000).

12/29/2023, 11:21 AM | Drop | Reason: [{LED=250 2.1.5 RESOLVER.GRP.Expanded; distribution list expanded};{MSG=};{FQDN=};{IP=};{LRT=}]

12/29/2023, 11:21 AM | Deliver | The message was successfully delivered.

More information
Message ID:******@SI2PR06MB5116.apcprd06.prod.outlook.com
Message size | From IP | To IP
‎139.13‎ KB | xxx.xx.xxx.xx | null

If I create a distribution group from ECP, it works normal.
Please give me some advice, thank you very much.

Answer 1

Hello Jack,

Considering the situation you described, please check to make sure that the "Send copies of group conversations and events to group members" option is selected.

I conducted the same test in my environment and proved that the email can be received normally. Therefore, it is recommended that you complete the above settings before testing.

If the problem persists, we recommend that you try deleting and re-adding all members to see if the problem is resolved.

Answer 2

Hello,

Welcome to our forum!

Based on your description, I would like to confirm that if the users cannot receive emails in Outlook client or OWA? Will the external sender receive the NDR, or will the members of the distribution group receive the email but with a delay of a few minutes?

Normally, the DROP event you see in the log, it just means that it has finished expanding, that is to say, the email sent to the distribution group has been expanded to every recipient in the group, and the members in the group did receive the email individually.

If the group members cannot receive emails from the sender normally, then it is recommended that you check the delivery management settings of the group to make sure it can accept mails from all senders:

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