mail returns with error of being undeliverable.

[Dallasdoo]

Hi,
In Outlook 2003 I send E-mail, immediatly it returns as undeliverable error,
resend mail o/k but it shows up as being sent twice in sent folder. I have
tried a repair, uninstalled and reinstalled Outlook 2003 a few times to see
if I can fix. I also have a backup folder for Outlook would this keep giving
me the same settings back?

Regards,

Rick Dallas.