How to resolve undeliverable issue

Question

Hello. Please forgive me if I don't explain this well. In Microsoft 365, there is a distribution list created. In that distribution list, there are mail contacts that was added along with other users who are actual employees of a company. The mail contacts are external users. When one of the mail contacts sends an email to the distribution list, they get an email saying that their email could be delivered to the other mail contact in the distribution list. However, all internal users on the list received the email. Is there a way to resolve this?

Answer 1

Hi @Kareem ,

When one of the mail contacts sends an email to the distribution list, they get an email saying that their email could be delivered to the other mail contact in the distribution list. However, all internal users on the list received the email.

If the mail is sent individually to the external members of the group, can they receive the mail?
And what if the mail is sent by others, like other external users which is not a group member, or by an internal group member?

In case it's due to the configuration of the ReportToManagerEnabled and the ReportToOriginatorEnabled parameter of the distribution group, please connect to Exchange Online PowerShell and check if the value of these two parameters are the same as below, change the setting using Set-DistributionGroup when necessary.

Get-DistributionGroup <DLIdentity> | fl *report*

If the issue persists, it's suggested to run a Message Trace in the EAC and see if more clues can be found. By the way, since it's a public community, I've edited the image you posted earlier by obfuscating the email addresses.

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