We have a few sites that require external access at the folder level. The external user has to be in Active Directory before adding to folder permissions so we created a new group 'External Users' and added a few in there. They do not show up in the group until the invite is accepted. Is there a way to be notified when an external user accepts a SharePoint Group invite?
There is no OOB way to know when exactly an external user accepts an invitation. However, we can poll an Azure AD Security group every several minutes using a Power Automate flow. We can detect if there are any new members in a group since the last run.
This is a quick unfinished example, but should give you an idea of how to implement it:
I would create a SharePoint list that will store all processed external users. If an AD Security group has a new member that is not yet in the SharePoint list, then, we can send an email alert.
Please following steps:
First, you have to create a Microsoft 365 group in Azure Active Directory
Then, sign in Microsoft 365 admin center as a global administrator. Navigation to Groups, and click Active groups, and find the newly created Microsoft 365 group.
Finally, click on the group. Then go to the "Settings" and turn on the "Allow external senders to email this group" option.
So, when you add an external user to the group, the external user will receive an invitation email.