I located the following technical document regarding attestation by e-mail responses, however I'm curious to know if this is possible in environments that do not have on premise Exchange, but have Exchange Online that is synchronized to AD without Identity Manager.
The ideal scenario is that approvers are able to respond to an attestation request by e-mail on their mobiles, and to avoid the need for authentication within the internal network.
If this is not possible, are there any other recommended methods to approve or deny attestations without requiring the approver to located on the internal network?