I recently ran into a similar problem using Blat (SMTP emailer). We found that our virus scanner (McAfee) console had port 25 blocked for this type of access. If you have a virus scanner you may want to check out what it does. This one allows you to uncheck that feature. After I did so, all was well.

Dana

>>>If I send mail directly from Outlook Express though, those emails will successfully be delivered. I am still researching this. I have verified the IUSR_ and IWAM_ write permissions to the mailroot folder and I verified the default smtp Virtual Server settings.<<
>
>I had already opened port 25 in the XP sp2 firewall. Upon further brainstorming I remembered there is another firewall in the router, so I opened port 25 there too, but same 'Relay' problem.
>
>Thanks
>G