I believe I have the same issue as jaybarr and hatchlingonline.
- Email notifications are not being sent if the backend/form admin "To:" field has an email with the same domain as the site. The warning error, "Failed to send your message. Please try later or contact the administrator by another method." is displayed on form submission.
- Emails have difficulty being sent if the frontend Email field has an email with the same domain as the site. The success message is displayed on form submission but there is a delay with the email being received. Also, the received email could not resolve the correct "From" client email address (firstname.lastname@example.org) in the header info; instead displaying something along the lines of "email@example.com".
In both cases, the data submitted by the form is still being received by the database (seen via the plugin Contact Form to DB Extension).
I'm thinking these issues are related to the fact that the site is hosted on one host provider (BlueHost) and that the client's MX-Records resides with another host/service (?).
Any thoughts or suggestions based on the info? I will try a couple of things and will report back if I have any success.