Changes

[https://wiki.mozilla.org/Thunderbird:Pluggable_Mail_Stores Pluggable Stores] explains very nicely why we needother pluggable stores. [https://mozillians.org/en-US/?next=/en-US/u/rkent/ R Kent James (:rkent)]'s project was to make our existing test suite topass successfully with maildir enabled as the default mailbox storage format. Maildir is the first pluggable mail store to be implemented as an alternative to mbox - the traditional format used by Thunderbird. Thunderbird's maildir implementation allows a single unique filename per email ([https://en.wikipedia.org/wiki/Email#Filename_extensions EML]). '''HOWEVER, note this is NOT full maildir in the sense that most people, particularly linux users or mail administrators, know as maildir.''' You cannot point a Thunderbird account to a mail server directory. You do not get message flags stored with emails. You only get a single file per message, and nothing more.