I am unable to reply to messages in my outlook express. I can send new messages and receive messages but can't reply. Any help would be appreciated.

What happens when you reply to a message?

The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was 'buddyf@accessky.net'. Subject 'Re: The house that golf built', Account: 'mail.bellsouth.net', Server: 'mail.bellsouth.net', Protocol: SMTP, Server Response: '550 relaying mail to accessky.net is not allowed', Port: 25, Secure(SSL): No, Server Error: 550, Error Number: 0x800CCC79



Any idea to stop this?

   It could be a bad email address.
   If it does that with every email, no matter what email address it is sent to, it is probably a problem with your internet provider, the smtp server (if it is different than your internet provider), or your settings for smtp.  Call your internet provider and ask them about it.  They should be able to fix it.