Where do I find documentation on the Sun protocol providers?
The Sun protocol providers for IMAP, POP3, and SMTP support many features that are not part of the JavaMail API specification. The documentation for these protocol providers is included in the JavaMail javadocs. The package level documentation for each protocol provider package describes the properties that are supported by the protocol proivder. In addition, the protocol providers include some classes and methods that applications can use to take advantage of provider-specific features. Note that use of these properties, classes, and methods renders a program non-portable; it may only work with Sun’s implementation of the JavaMail API. See the IMAP, POP3, and SMTP package javadocs for details.
