When we respond to helpdesk calls our users are no longer receiving emails.

We have been using servicecamp for some time and as the Support engineer we respond to tickets. Recently end users are not receiving the responses.

We use O365 email and it doesn't appear to be stopped by any filtering or junk filter so it seems it is not leaving servicecamp.

Is there a log of emails it send or way to test if the emails are somehow failing. i.e. a non delivery report from the servicecamp system?