Does anyone know why I otrs would have issues with sending notifications?

Wed Nov 17 17:14:18 2010 notice OTRS-CGI-10 Sent agent 'OwnerUpdate' notification to '*****@power-soft.net'.

Wed Nov 17 17:14:18 2010 error OTRS-CGI-10 Can't send message: 550Start mail input; end with <CRLF>.<CRLF>

Mik