Configuring Outlook Express to work wth Claranet

[Briain Boruhma]

Trying to set up OE to work with clara.net with whom I have an NG account
and email addy.

Keep getting the following message or variations thereof.

The message could not be sent because the server rejected the sender's
e-mail address.
The sender's e-mail address was 'na...@clara.net'. (totally valid)!!
Subject 'More Testing', Account: 'pop.clara.net', Server: 'relay.clara.net',

Protocol: SMTP, Server Response: '550 relay not permitted', Port: 25,
Secure(SSL): No,
Server Error: 550, Error Number: 0x800CCC78

Can log in via webmail or via usual mail client but not OE.

Any ideas please.

TIA

Briain.