What environment are you running in? In a Web Server? Low permissions environment? Across a network?

It's an infrastructure problem...

You can also use nMailMode = 2

which doesn't use the .NET features, but raw Win32 socket code. It doesn't do a few things like SSL/TSL connections to a server however - for that you need nMailMode = 0.

+++ Rick ---

>Hello.
>
>We recently switched from MAPI to SMTP to send email. Now on one of our customers computers we get the error message:
>
>Unable to create SmtpClient due to missing permissions. If you are using a port other than 25 for your email server, SmtpPermission has to be explicitly added in Medium Trust.
>
>Has anyone else seen this and how can I fix this?
>
>Thanks!
>
>-Greg