Autor: Always Learning Data: A: Exim Assumpte: Re: [exim] Produce 550 error depending on sender's email
> We need to send a 550 error to several senders even though the recipient
> email address is, in fact, valid. This is because the recipient does
> not want to receive any email from the sender and wishes them to think
> that their email does not exist on our receiving servers.