• MailMessage class
• MailAddress class and MailAddressCollection class
• SmtpClient class, SmtpPermission class, and SmtpPermissionAttribute class
• Attachment class, AttachmentBase class, and AttachmentCollection class
• SmtpException class, SmtpFailedReceipientException class, and SmtpFailedReceipientsException class
• SendCompletedEventHandler delegate
• LinkedResource class and LinkedResourceCollection class
• AlternateView class and AlternateViewCollection class

This is a completely new namespace.  The old System.Web.Mail namespace has been deprecated.  This new implementation is not dependent on CDO.  Dr. Peter Bromberg has an introductory article on the new features.  There is also the infamous www.systemnetmail.com site.

MailMessage class - Represents an email message.  New properties for this (compared to the properties in the web.mail version) are DeliveryOptions, ReplyTo, and SubjectEncoding.  There is also support for AlternateViews - allowing you to send both text and HTML representations of the email.

MailAddress class - Represents an email address.  Address, DisplayName, Host, and User are readonly properties of this object.  Properties are set in the constructor.

MailAddressCollection class - Collection of MailAddress objects. 

SmtpClient class - This class sends email via SMTP.  It is not dependent on CDO, it can work over SSL, and the send can be performed async.

SmtpPermission class - This class regulates whether or not an application can send mail via SMTP.  Access can be locked down to no access, only via the default port (25), or unrestricted.  What's interesting is that this class doesn't appear in the Create Permission Set wizard.

SmtpPermissionAttribute class - Attribute implementation of the SmtpPermission class.

SmtpException class - Exception that is thrown when SMTP Client can't complete a send or sendasync operation.

SmtpFailedReceipientException class - Exception that is thrown when a receipient is not valid.

SmtpFailedReceipientsException class - Exception that is thrown when an email can't be sent to ALL of the receipients.  "This class supports the .NET Framework infrastructure and is not intended to be used directly from your code. "... The following statement from the remarks in the documentation contradicts the explanation: "The InnerExceptions property contains the exceptions received while attempting to send e-mail. The e-mail might have been successfully delivered to some of the recipients."

SendCompletedEventHandler delegate - Delegate that is called when an async send is complete.  Handles the SendCompleted event.

LinkedResource class - Represents an embedded resource in a message, such as a HTML image.

LinkedResourceCollection class - Collection of LinkedResources.

AlternateView class - This class is used to represent an alternate view of a mail message.  This would likely be an HTML version of the email. 

AlternateViewCollection class - Collection of AlternateView objects.  This is used in the AlternateViews property on the MailMessage object.

Next up -> GDI