Enrolment

My students are attempting to self-register in my courses but are not receiving the required confirmation email. When setting up my courses in the last few weeks I tested this procedure and it worked fine for my sample students. Now, however, no-one is receiving a confirmation email, including test students that I have created similar to those that did work a few weeks ago. Various email services are being used by my students so I am confident it is not a case of spam filters blocking the emails. I have not changed any Moodle settings or server settings in the meantime (and have checked and re-checked this many times just in case).

I have found other forums that have discussed this issue in the past, and have checked SMTP host settings and similar things suggested in those. These seem to be as they should be and I have found no satisfactory explanation or solution. I can find no good reason why this should not be working now, particularly given that it was working just a couple of weeks ago. Is this a bug in the system or am I missing something?

Thanks in advance for any clarification or assistance.

Chris