The above interfaces are used to access mailboxes from the mailbox store. The mailbox is modeled as described in SMTP RFC and Internet Message Format RFC.
In short, a mailbox can be used to refer either:
- a character string that represents an email address
- a store; a place used to deposit a user's emails
Not all emails hava an associated store, for example email aliases do not.
A more detailed explanation can be found on wikipedia.
For best results check out the latest RFC documents.
The project is hosted at http://code.google.com/a/apache-extras.org/p/mailbox-hdfs/. The sources are managed using mercurial and you can build them using Apache Maven.
 RFC 5321, Simple Mail Transfer Protocol, J. Klensin, The Internet Society (October 2008), Section 2.3.11 (Mailbox and Address)
 RFC 5322, Internet Message Format, P. Resnick (Ed.), The Internet Society (October 2008), Section 3.4 (Address Specification)