We have been randomly not receiving contact forms submitted over the past 2 year of using 3dcart.

I've realized that is based on email address.

Example:
https://www.morepowerdiesel.com/contactus

Customer email:
[email protected] and hit submit = confirmation but no email is ever received
[email protected] and hit submit = confirmation and email is received.

There has to be a filter or validation somewhere within 3dcart or the mail asp that sets what is an acceptable email address.

Any help is appreciated.