i tested an unauthorized send through modular.sommba.co.uk using outlook express, and i got
The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was 'danielpritchett@yahoo.com'. Subject 'test', Account: 'mail.directvinternet.com', Server: 'modular.sommba.co.uk', Protocol: SMTP, Server Response: '550 5.7.1 Unable to relay for danielpritchett@yahoo.com', Port: 25, Secure(SSL): No, Server Error: 550, Error Number: 0x800CCC79
is modular.sommba.co.uk your server? it says it's not able to relay for my address. i had that problem, so i installed a small smtp server on my machine, and changed my php.ini to read
SMTP = localhost