Good evening David and welcome back!
Thank you for reaching out to us.
I would love to help you with this topic.
As a first troubleshooting step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
With that in mind, even if a user does not register for your site, he typically needs to fill out the customer info. In turn, that really creates a “customer” WordPress user.
So in short, the emails should still go.
You can have the system send tickets from any chosen email address by simply installing, configuring and testing the following plugin: https://wordpress.org/plugins/easy-wp-smtp/
Using a real SMTP server with authentication will bypass the built-in WP mail functionality altogether.
Please make sure you configure and test the settings using the plugin’s built-in tool.
This usually solves issues with emails not being sent.
Let me know how that goes.
Best regards,
Geoff B.