RingCentral will not send SMS containing some email addresses

I am having issues with RingCentral not sending SMS messages that contain certain email addresses. I have a domain address for my small business and RC will not send messages that contain our email addresses that use the business domain. I can send SMS with email addresses like Yahoo, GMail, or iCloud. It also will not allow us to send a link to our website that is at the same domain address. How do I fix this?