There is no other functionality built into .NET that allows you to send email other then the System.Web.Mail namespace which uses SMTP.
CDONTS has been depreciated and shouldn't be used, however, you might be able to add a reference to the CDOSYS.dll in your project and make calls to it to send email for you, though I wouldn't recommend it.
Lastly, you could create a dll of your own that connected directly to a mail server and you could then send email using which ever protocol is set up on that server.
Read this if you want to know how to get a correct reply for your question:
^^Took that from planoie's profile^^
^^Modified text taken from gbianchi profile^^
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