Class List
Here are the classes, structs, unions and interfaces with brief descriptions:

SmtpClient | SmtpClient namespace holds all public definitions in the SmtpClient module
Attachment | For backwards-compatibility only
Message | For backwards-compatibility and convenience
SmtpClient | Class that's used to communicate with an SMTP server and supports optional TLS/SSL encryption
SmtpConnection | Class for SMTP connections; returns an object of class SmtpClient for sending emails