Email issue—Blocked Email

When trying to reply to an email from with my on the mail app I received: “We’re sorry, but your email message to “ didn’t work. Your reply was sent from a blocked email address. Try sending from another email address or contact a staff member.”
Also, I am unable to add my address to my forum account (do not receive a confirmation email). It would not accept it during original setup.

Regain your privacy! Adopt /e/ the unGoogled mobile OS and online servicesphone

Pl can you send a mail to with the details.