Email approval not being processed by Active Roles service (Outlook add-in) (4281958)

Approval workflow is configured, but when the manager approves the request via email (OWA or Outlook add-in) the approval does not get processed by the service and the approval request remains in a pending state.

The following Event ID 1533, can be seen in the Windows Event logs for the Active Roles Administration service:

Active Roles Administration Service encountered a problem when processing approval response received via e-mail.

Exchange Web Services address: https://web.contoso.com/EWS/Exchange.asmx

Active Roles mailbox: ARS-Mailbox

Approval task: 0-000000-0

Details:

Sender of approval response cannot be identified from the response message.

This is caused by an email id being referenced in multiple user objects. I.e.: the same email address listed on different user accounts. This includes user accounts in different managed domains.

This is not a supported use-case in the approval flow, as it leads to an ambiguity. 

SOLUTION

Make sure that all approvers involved in the approval process hold a unique email address (email id).