Yes, trying is the exact word Mary. I haven't found luck and I've scour the whole forum for solution to no avail. i've read the documentation and spent a couple of month before posting here.
We are hosting our own Moodle.
one scenario that didn't return an error was removing the smtp settings, but the emails are not being sent to the registrant for confirmation or don't receive anything at all :/
If you are using Debian and or Ubuntu server, then if you leave the smtp field blank Moodle uses the PHP mailer. This has some down sides as php looks for Sendmail and that is not default. The very best way is to point your Moodle mail at your domain SMTP host, putting a password and user in if required.
The other reason your mail could be stuck is, your smtp host is not configured to accept mail from your Moodle, simple check. Get admin to run a mailq and see what happens.
The last of the obvious reasons, your smtp host uses and enforces TTL/SSL and Moodle is configured to use plain text.