Sending Mail with Outlook Express

[Ranter]

I have installed outlook express on my home computer using exactly the same settings as I have with my PC at work. Why then does my home system often decide it won't send certain mesages? It will not send certain mail messages and the messageI get is that the server has rejected them. Does anyone know why this should be?

[Ghost_Hacker]

What is the exact error message?
Is the mail server hosted by your employer or by an ISP?
Do any emails sent to this server get thru?