For Microsoft 365.
The e-mail address which are addressed to outside of company included group address does not seem to be filtering. Are there any limitations?
When you send an e-mail to the group address of the Microsoft 365 (including external address), it flows as below:
1. Send an e-mail from Microsoft 365 to the group address.
2. Distribute the e-mail to each member of the group address within the Microsoft 365.
3. If the group address distributed to...
a) inside of company:
The e-mail is sent in the Microsoft 365.(Same as the individual addressed in-house)
* It is not through our filtering service
b) outside of company:
The e-mail which is included a mailing list (distribution group, security group, dynamic distribution group) to be sent to an external address after the distribution is going to send as the Envelope From is Null (empty) by default specification of Microsoft 365.
* Although the e-mail is passed to our filtering service, the Envelope From address is empty.
Our filtering service determines the value of the Envelope From for the filtering rules.
For this reason, the e-mail will be out of our filtering service if the Envelope From address is empty.
It is possible to change the behaviour of default specification of the above Microsoft 365, you can also apply to use a filter on changing default setting.
How to Set:
Change the ReportToOriginatorEnabled to “True” at Powershell
The Example of Command Execution:
Set-DistributionGroup -Identity <Group Name> -ReportToOriginatorEnabled $True