Whatever you do under the esa.XX domain, postmaster@esa.XX *must* be a valid address. Who tells ? Just because it's a domain name it need not be a valid (domain part of a) mail address - unless there is an MX. At least under .NL it is a hard requirement that postmaster@domain.nl be a valid address. Have you ever tried postmaster@ac.uk ? ac.XX, co.XX, etc. are artifacts, not domains; the real domains go one level lower. Crazy idea: if company X moves from Cologne to Darmstadt, its domain name would change, they would have to reprint their letter heads, business cards, etc., and someone would have to cope with all the bounces of mails sent to the old domain name... Totally correct. If the company moves, they will have to change their business cards, letter heads ... PTT's take care of forwarding letters. Who is going to take care of forwarding e-mail? Piet