There was a thing for AX2012 called "Axnosis WF Email Approver". The main differentiator to the standard e-mail approval was the ability to reply to the mail in any POP mail client instead of clicking links or buttons:
How to action a Dynamics AX 2012 work-item received by email.
Step1: Access your workflow email notification via your mail client e.g. Microsoft Outlook, Blackberry Email etc…
Step2: Your email should have a number of action links supplied if you have setup your workflow template correctly. Click on the action that you would like to perform e.g. Approve. A new email dialog should appear with a recipient such as workflow@[yourcompany.com] with a customized subject for the workitem such as “APP1234” or “DEN1234”. Do not remove either of these.
Step3: Add a relevant comment to the action you are performing by appending it to the subject or adding it at the beginning of the email message E.g. “APP1234 Please proceed with the order” or “DEN1234 Over Budget”
Note: If you are performing an action that requires you to choose a user (request change and delegate), you need to append a valid email address to your signature e.g. REQ1234 bobby.jones@[yourcompany.com] if no email address is specified one will receive an error response from the system e.g. “No delegate user specified for action type…”. This email address needs to be linked to a user in AX under User Options.
Step4: If you are using the body of your message to add a comment, or would not like to add a comment at all, please remove the signature from your message so that workflow doesn’t add this to or use it as a comment.
Step5: Click send. You should receive a confirmation email within a couple of minutes from workflow stating that your workflow action has been successfully completed. You may also receive a notification stating that the action was unsuccessful. See the section below on how to deal with these notifications.
In the meantime this customer of ours let it be implemented in D365FO from scratch. The core is a listener within D365FO reading a mailbox and interpreting the mails. Should your implementation in MS Flow be limited, I can give you the contact and I am sure the customer is going to be more than happy to sell this development.
