The user receives the email notification but when replying the email with the actions "Approved" or "Rejected", the task is not actioned.
The service account mailbox does receive the email reply by the approver.
There were entries in the K2HostServer logs indicating that there is some security prohibiting emails from being processed.
"MessageBus","61011","SpamMessageIgnored","ExchangeWebServicesOrigin","61011 Message AAMkADFiZmFkMmYwLWQ2ZWUtNDE0Ny1iZjRmLTNlMzVkZjQwOTA2NgBGAAAAAAA3uwD8PS1WR5wKma6p1gP7BwBZDP63XlFOSrwLbdlmW26sAAAAAAEMAABZDP63XlFOSrwLbdlmW26sAAAOwEBtAAA= ignored due to spam restrictions."
1. Make a backup of the K2HostServer.exe.config file before modifying it.
2. Remove the add domain line.
3. Save and close the file.
4. Restart the K2 service.