Is there a way for me to receive an email from mydomain@whoisprotectservice.net, even though the domain owner has recently switched registrars?
 I've tried sending a letter, but it hasn't been successful. Unfortunately, I don't have the ability to change the account owner.

One solution is to reach out to the registrar that is currently in possession of the domain and ask them to manually send an email verifying the transfer.
I myself faced similar issues and found that the only way to resolve it was by contacting the receiving registrar's support team.

Also had a similar problem. Decided after contacting the registrar.