I am trying to add an existing AD group to an alert for a list, however, it does not appear in the dropdown.
When I add the email directly i get a
"Sorry, you are not allowed to share this with external users."
I checked and each user has an email with
The group is set as a security group, and as I mentioned, it has an email address.
What could be preventing the AD group from populating and being accepted. This is for a SharePoint 2013 On-premises installation.