Relevant Product: Exclaimer Cloud - Signatures for Office 365
Scenario
When configuring signatures in Exclaimer Cloud, you notice that you cannot select groups that are present in Office 365.
Reason
Only mail-enabled security and distribution groups are supported.
If the group is mail-enabled but still not visible, please try and perform a data synchronization as per this article: User data or group membership updates are not reflected in Exclaimer Cloud.