Hi Dr Numerof.
I had to double check with Updox about that. According to them, DirectTrust is the national standard for secure record transfer and direct email. Most companies use them for direct messaging. Here is a link to the list:
https://www.directtrust.org/member-list/According to them, you will be able to receive messages from any secure address, but you will not be able to send to an address not on the direct trust.
