An issue, which I thought had been fixed, with sites using the Trend Micro spam-blocking service blocking emails from this Moodle is now occurring again. This problem applies particularly to the NSW Department of Education and Training.
Both ASTA and our Moodle host, Pukunui, have tried to get Trend Micro to put this site on their white list, but this seems not to be possible because of company policy.
We will continue to work on this issue, but I would suggest Moodle users who want to participate in forum discussions should change their account email addresses to one that isn't associated with Trend Micro.
Apologies for this inconvenience.