Some email servers will not send emails that aren't FROM a valid email address from that server. Try setting the FROM to an email address like:
webmaster@yourdomain.com (and make sure it is a valid email address).
It could also be that the recordset you are using for the TO address isn't working properly.
I'd try getting it working with a hard coded TO and FROM and then change them to dynamic values one at a time to narrow down the problem.