Hello
Thank you for posting in Q&A forum.
Even if both groups belong to Active Directory, you can only see which groups they belong to in the user interface, or which groups you belong to/which groups you own or members in the group, and you can't see the status of another unrelated group through one group.
If one belongs to Active Directory and the other belongs to Mail, you can't through Active Directory to know that your users are group members at other programs. Because they are two different system, Active Directory only allow you to verify the user's identity information from the DC, and Active Directory will not and is not allowed to read the data of other programs
If you can assign AD group to this application, then is means that this application can get the information from the DC. If you assign a Mail group, you can try to assign to see if this application can get user information from mail server
Best Regards,
Yanhong Liu
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