Confirmation Emails Are Not Received

Customers registering at some of my client sites are not receiving the confirmation email.

I believe I have it set up correctly because the test email in Joomla Global Configuration works, AcyMailing works, and DT Register works. I've also checked to be sure I have email set up correctly in cPanel.

I tried a different site this morning and it sent an email, but it took almost an hour to be received. The Joomla, AcyMailing and DT Register emails all came in almost instantly.

Is there something obvious I missed in setting up CB on this site?

Thank you,
Ernie

Joomla mailer falls back to phpmailer if it fails. So if you're using SMTP and it fails it'll silently fallback to phpmailer, which might work. CB does not do this and instead errors. Try emailing your self within CB > User Management by selecting your users checkbox then clicking mass mailer to see if emails from CB are working in general or sending in a timely manner.

I tried Mass Mailer and it failed:

Error sending email: SMTP connect() failed. github.com/PHPMailer/PHPMailer/wiki/Troubleshooting

I'm using SMTP with the customer's domain email address.

Oddly, I have several other sites set up with SMTP. I tested one, and it quickly sent the email to me.

I changed to PHP Mail and it worked.

But for future reference, what might be the reason SMTP didn't work for this site but worked for the other site?

Thank you,
Ernie

Most likely you've a domain mismatch with the SMTP host and its SSL certificate, it could also be a domain mismatch from the senders email address compared to the SMTP host, or it could be the credentials are invalid.