When I was developing my ASP.Net app on local machine,  I had no problem sending email by calling directly the SMTP relay server assigned by my hosting company Winhost, with port set to 587 of course. But when I deployed the app to the winhost server, the email tool threw this exception :

Request for the permission of type ‘System.Net.Mail.SmtpPermission, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089′ failed.

I did suspect some some security permission to Smtp related assembly and have done some search toward that direction. First I got a lead from some post via Google search and one suggested added this entry into the <system.web> section; but that did not work, so I am not going to give reference to this post.

<securityPolicy>
<trustLevel name=”Full” policyFile=”internal”/>
</securityPolicy>

Today, I went into Windost support site and did another search on their forum, and they pointed me to using this instead:

<system.web>

<trust level=”Full” />

</system.web>

Yes, that was all it needed!