Emails to users not send by CBPHPMailer

Please see attaches screenshots   

Clear the reply-to address and retry.

Just retried to sent by use of the mass mailer, no incoming messages.
The PHP mailer test from within the global configuration is OK.
Attached the PHP mailer settings in the global config and the CB pages setting general and registration for your info.
I hope it helps..     

If the mailer isn't erroring it's being stopped at the mail server not in PHP. Am looking into removing our PHPMailer as it's a bit of a leftover from Joomla 1.x days that we don't really need anymore. I do not have a timeframe when that will be done. I suggest contacting your host and seeing if they can check mailer logs. It's possible your host might also recommend SMTP over PHP Mail. I don't have anything further to suggest at this time.

Support from my provider confirmed no issues with the PHP mail server and replied the bug could be caused by the update of the PHP version 8.0
As the PHP mailer 6.6.0 (used by other extensions) is working fine, would it be possible to reroute the settings in CB configuration for use of the other PHP mailer?

It's not caused by PHP 8. My development environment has been PHP 8.1 for months and 8.0 for months prior to that where the email is working perfectly fine. You can try using SMTP within Joomla's mailer settings and CB will use that as well. There is not a way to configure CBs mailer separately.

I've already a pending merge request to switch CBs mailer entirely over to Joomla's. Once reviewed and merged (we use peer review in our team) there won't be a CBPHPMailer anymore. This likely won't be until sometime next week as Beat is taking some well deserved rest this week.