I’m sorry you’re having a bad experience with the emails. I know it can be frustrating and a bit counter-intuitive, but the vast majority of problems come from particularities in email server configuration. I’ve made several adjustments over the years to improve compatibility for as many users as possible, but it will still need coordination with the web host in some cases.
If you’re getting other emails from your WordPress site, the most likely issue is going to be with the specific headers being sent out by this plugin. I’ll assume you’ve checked each of the points in the email delivery checklist in the FAQ. Here’s a run-down of what the headers look like, which you should be able to use to narrow down the source of the problem.
1. All emails sent by this plugin include a FROM header which uses the email address defined under your general WordPress settings (Setting > General > Email Address). This is done to ensure wider compatibility with SPF policies, but may not be appropriate for your server depending on it’s particular configuration. (If you’re receiving other emails, like new user notifications, this probably isn’t the issue.)
2. Emails sent to the user include a TO header with the user’s email address and REPLY-TO header with the email address defined under Bookings > Settings > Notifications > Reply-To Email Address.
3. Emails sent to the admin include a TO header with the email address defined under Bookings > Settings > Notifications > Admin Email Address and a REPLY-TO header with the user’s email address.
You can read the code which produces the headers and it’s all passed through WordPress’s core wp_mail() function.
If you find other emails are sending fine, the most likely problem is with the specific FROM and REPLY-TO headers. These could be conflicting with SPF/DMARC records on your server. Other issues could be that the content of the emails is flagging up as spammy and being blocked by recipient servers.
Your hosting company should be able to look at your email server logs to see if emails are actually getting sent out and, if not, why not. In some cases, when emails are blocked by recipient servers, your host may have logs indicating why.
Email is becoming more and more difficult to deliver reliably, which is why I use and recommend a third-party mailing service. Having said that, if you want to dig in further, I’ve written an article about what can cause delivery problems:
How to solve email delivery problems with WP Mandrill
A more detailed and technical article that goes into SPF and DMARC records is here:
SPF, DMARC, and DKIM Oh My! Our Top Tips to Keep Your Email Out of the Spam Folder
I’ve made a note to extend the plugin’s documentation with some of this information. Unfortunately, there’s not much more I can do on a general basis because everyone is working within a different server configuration,.
If your host comes back with specific information about what needs to be changed, I’m sure I can help you figure out how to do that.