Hello,
Thanks for your message. We understand the situation, but our plugin simply builds the email message objects and hands them over to the WordPress native functions that will take care of sending the actual email message. This means that from our plugin you can only ensure the email message object will not cause a rejection by your mail transport agent during the sending operation handled by the WordPress native functions.
Most mail services, PHP Mail on your server or an SMTP service, will refuse to send an email message when the sender email address is outside your domain scope (should be [email protected]), or whenever the sender email address is equal to the recipient email address. This is something you can check from the Configuration page of our plugin, beside when the email messages should be sent (rental order status “Confirmed” or also when on “Pending”). However, these are the only useful settings in our plugin that may affect the email sending results.
Any other issue should be checked either from your own server, or by installing some third-party WordPress plugins that keep track of the email sending functions. You can eventually consider using a third-party plugin to establish an SMTP connection for sending the email messages.
We hope this helps!
The VikWP Team