I send email through Outlook using VB.Net 2005; this is working fine.
At the same time, however, I receive the following message:
A program is trying
This is "by design". It's done to prevent viruses from doing things like going through the address book and automatically sending emails on the user's behalf. Having the dialog prevents a virus from silently becoming a spam bot.
I know this isn't answering your direct question, but is there a reason you can use the System.Net.Mail.MailMessage class and send using that? Or is this because you want the e-mail to show up in their sent items?
You need some library like Redemption to circumvent this popup. It's the default built-in security behaviour of Outlook (since version 2002 I think).