That doesn't look like the entire (complete) error message; usually, there is also included some other information (for example: Task ‘mail.domain.com - receiving’ reported error (0×800CCC0F), or some other variation).
If you can receive ok, but not send, it is likely to be a configuration error. Possibly your ISP is blocking port 25, or your authentication settings might be wrong - it really hard to tell with just that message and nothing else.
Have you reviewed the Outlook set up information on the DH wiki, as well as the general Email Getting Started information? What ISP are you using (it might help us research your proper port usage)?