I'm sending to < removed>,however ,it is refused as if it was sent to<removed>It is a legitimate email every time. This has been going on for three months! I've ask the Postmaster but no reply! This needs to stop! This seems to be the only one to which this happens!

Sounds like your address has been blacklisted for whatever reason.
You need to discuss this with the mail provider.

Have you tried to send an email there, from different email address. Perhaps they have blocked your email address.

Also, if this is a email address from a paid account. Perhaps the account is not current

Could be a hijacked account or any number of bad reasons, and you shouldn't be trying over and over!

Have you contacted the other person by a different means such as telephone, in person, text, etc. to find out if they are blocking you? Do they consider contact from you to be 'legitimate' or is there something you have left out?