No. server error 530 error no. 0x800ccc78?-Collection of common programming errors

That error is: “Unknown sender. This is caused by having the incorrect e-mail address in the Reply-To field.”

The e-mail address of the person you are trying to send to is somehow unknown or unrecognised as a valid e-mail address. So that mail may be in your outbox and everytime you are in outlook express and it tries sending the mail it will give this error. So try deleting it from your outbox so it stops trying to send it or check the e-mail address and see if you have it correct then resend it.