Article ID: 2723654 - View products that this article applies to.
In Exchange Online in Microsoft Office 365, when users send email messages to a distribution group that contains external recipients, the external recipients don't receive the messages. Additionally, senders don't receive nondelivery reports (NDRs).
This issue occurs only when the messages are sent to the distribution group. When users send messages to the external recipients individually, the external recipients receive the messages.
By default, the ReportToManagerEnabled parameter and the ReportToOriginatorEnabled parameter are set to True when a distribution group is created in Exchange Online. When the parameters are set to True, the Return-Path field in the header of the message is <> (blank). This means that the remote messaging system will not send delivery reports to the user who sent the message to the distribution group.
Additionally, if spam filtering is enabled on the remote messaging system, the message is dropped, and delivery reports are suppressed. This occurs because some anti-spam devices might flag messages whose Return-Path field is blank and not let the messages be delivered.
To resolve this issue, take one of the following actions, as appropriate for your situation.
If the user isn't sending the message as the distribution groupIf the user isn't sending the message as the distribution group (that is, if the email address of the sender and of distribution group are not the same), set the ReportToOriginatorEnabled parameter to False. When you do this, delivery reports are sent to the sender.
To set the ReportToOriginatorEnabled parameter to False, follow these steps:
If the user is sending the message as the distribution groupIf the user is sending the message as the distribution group (that is, if the email address of the sender and of the distribution group are the same), set the ReportToManagerEnabled to False. When you do this, delivery reports are sent to the user who is specified in the ManagedBy attribute of the distribution group. By default, this is the user who created the group.
To set the ReportToManagerEnabled parameter to False, follow these steps:
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