Send it certified mail, return receipt requested if you are so inclined. 

I ended up changing my RA, and so now they're handling mail.

If possible, notify the renters simultaneously and do it in person.

Quote from @Max Kulishov: Have you guys gotten any deals sending direct mail?

E-mail with details has been sent your way.Also, thank you @Jonathan Greene for helping to point this to the right person for assistance.

I spent well over 1 mil on a CRM, owned a rock solid direct mail provider and drove a Rolls Royce.  

Has anyone had any problems using the C.A.R form with the "or ASSIGNED" and assigned to another person.And would I have to notify the realtor or selling parties that I have assigned the purchase agreement to another person or entity?

Because I sent them an e-mail and they sent me the link in the original post (https://www.cmha.net/housing/landlords/rent.php) that shows that amount.

Will mail be delivered even if A and B are not officially registered with the USPS?

Three weeks before the closing date, the wholesaler notified me that the house was going through probate and that we could not close until the first week of December.