[SOLVED] Problem with CB email sending

Yesterday, a person trying to register on our site through the CB sign-up form sent me a message that, at the end of the registration process, he was getting the following error message (see also attached):

0 Return value of CBLib\Cms\Joomla\Joomla4::getMailer() must be an instance of Joomla\CMS\Mail\Mail, instance of JMail returned

Additionally he did not receive an email confirmation, presumably because CB is no longer able to send mails due to the above error. What strikes me the most is the "Joomla4" element in the error message, since our site is still using Joomla 3 (V3.10.11). The latest version of CB (2.7.4+build.2022.10.21.15.41.28.56bdcdeab) is already installed.

Any ideas how this problem might be fixed? Your help is much appreciated.

Strange, JMail is just an alias for Joomla\CMS\Mail\Mail so that should not be erroring. Also works fine in my tests. What PHP version are you on?

Am also preemptively applying a fix. Normally an alias like that should work fine, but it might not under some PHP versions.

forge.joomlapolis.com/issues/9068

Thanks for your quick reply!
My PHP version is admittedly a "little" outdated... it's 7.4.30. You think updating to a newer PHP version might resolve the issue?
I'll try that. Thanks for the hint!

Thank you for that, too!

I just tried upgrading to a higher/newer PHP version on my test system (PHP 8.0.23 and then PHP 8.1.10). But in both cases I got the following error message on my Joomla backend:

0 Call to undefined function create_function()

Check within your server error logs and provide the full callstack for that error. We do have some plugins using create_function if it's available and only on older PHP versions, but if you've a really old version of a plugin installed that's using it then it's probably not compatible with your PHP version.

PHP 7.4 should be working fine though so you shouldn't have to upgrade to PHP 8 and it's not really recommended while still on Joomla 3.