Not all web hosts are set up to deliver email out of the box from your WordPress installation. Luckily, you can connect your MemberPress site to most of the top email services using our email integrations. This should dramatically increase the deliverability of your emails. Read more about membership email delivery on our blog.
If your customers aren't receiving emails, it could also indicate an issue with your payment gateway setup. You can find the instructions to integrate Authorize.net, PayPal, or Stripe by visiting our integrations listings.
Feel free to reach out to our support team if you continue to have trouble. We're happy to help!