privaterelay.appleid.com account is not working

I can't receive emails to my private account with the hide my email option:

Undelivered Mail Returned to Sender

This is a system-generated message to inform you that your email could not

be delivered to one or more recipients. Details of the email and the error are as follows:

<***@privaterelay.appleid.com>: host

smtp3.privaterelay.appleid.com[17.56.9.16] said: 550 5.1.1

<*******@**********>: unauthorized sender (in reply to RCPT TO command)

[Edited by Moderator]