I would go through this code:
http://sholliday.spaces.live.com/blog/cns!A68482B9628A842A!138.entry
so you can learn/understand ~~HOW~~ emails are sent via .Net.
When emails are failing , you need to get a grasp on the different
authentication models, which is the usual culprit.
AFTER you work through the code at the above URL....you can probably use the
default settings:
Here is the typical setup for emails. Again, if you just skip the URL above
and just go for the "quick fix" below, you'll miss the opportunity to
understand ~how the emails are sent using the different authentication
schemes.
<system.net>
<mailSettings>
<smtp from="(e-mail address removed)">
<network host="smtp-server.rr.com" password=""
userName="(e-mail address removed)" />
</smtp>
</mailSettings>
</system.net>
But it would be wise/prudent to get a grasp on how emails are sent instead
of just patching it so it works today. Because when you deploy, things most
likely will be slightly different.