MSN Explorer not sending emails

I transferred someone's filoes including their MSN setup to a new XP home computer.

She is using MSN Explorer for her emails etc. Now we are noticing that the emails are stuck in the outbox, are not being sent.
We emptied the outbox and tried sending a new email- same story. Of course using the Hotmail interface works.

Internet options are set to MSN as email client.
I have no idea where to tweak this MSN thing. Anybody...?

Thanks!