A JavaMail service provider is a driver that supports JavaMail interaction with mail servers using a particular mail protocol. WebSphere Application Server includes service providers, also known as protocol providers, for mail protocols including Simple Mail Transfer Protocol (SMTP), Internet Message Access Protocol (IMAP), and Post Office Protocol 3 (POP3).
A mail provider encapsulates a collection of protocol providers. For example, WebSphere Application Server has a built-in mail provider that encompasses the three protocol providers: SMTP, IMAP and POP3. These protocol providers are installed as the default and suffice for most applications.
If you have a particular application that requires custom protocol providers, first follow the steps outlined in the "JavaMail API Design Specification, V1.2, Chapter 5 - The Mail Session" to install your own protocol providers. This document outlines the process for the JavaMail 1.3 API as well as JavaMail 1.2. See the article, Mail: Resources for learning, for a link to the specification.
Mail sessions are represented by the javax.mail.Session class. A mail Session object authenticates users, and controls users' access to messaging systems.
To create platform-independent applications, use a resource factory reference to create a JavaMail session. A resource factory is an object that provides access to resources in the deployed environment of a program using the naming conventions defined by the Java Naming and Directory Interface (JNDI).
Ensure that every mail session is defined under a parent mail provider. Select a mail provider first and then create your new mail session.
Related reference
Mail: Resources for learning