title: JavaMail API and Tomcat 7 Implementation
body: <p>There are several Java EE APIs that exist as just that - APIs (interfaces, domain objects, enums, etc. but no actual classes that <em>do</em> stuff). APIs like JPA, JDBC or JTA. These APIs must then have implementations; for JPA there are impls like Hibernate, MyBatis or TopLink. For JDBC there are drivers for each specific RDBMS. For JTA there is Bitronix and Atomikos.</p>
  
  <p>But what about JavaMail? Is it just an API? If so, what are some common implementations of it? If I deploy my Java app (as a WAR) to Tomcat 7, where does this implementation come from (specifically)? Does Tomcat have its own JavaMail impl? What JARs/packages/classes compose the Tomcat impl?</p>