Not sure where to take this from here.
Yes, I definitely recommend premium support. However, I also want to be realistic and manage expectations here.
At this point, I’m not entirely sure its the plugin, but I also don’t generally rule things out 100%.
I can usually gauge an issue based on support tickets from users and also from my own personal experience (the support site rocketgeek.com runs the same version of WP-Members). I’ve just not been experiencing any issues with emails.
The plugin uses wp_mail() to send emails (as does WordPress, and many other plugins). The thing about wp_mail() is that it only returns a true|false boolean to tell you that the function ran to completion.
If “true”, at that point, the email has been generated, and handed off to the web server’s mailserver or your SMTP server (if using SMTP). But that doesn’t guarantee that things will be sent. Something could go wrong in that process as well.
So while I’d like to say that signing up for premium support would make everything OK, if it lies outside the plugin, I’m not sure how much help I can offer. That’s why I mentioned at the beginning here that I want to manage exceptions.
I think the best thing to do from here is to use an email logger. There are several on www.remarpro.com in the plugin repository. An email logger will be able to tell you if wp_mail() ran successfully and if an email was generated (which would be the important first step). You can install one of these and then do a test registration and you should have an email in the log that matches up with that registration.
Hope that helps.