Unpacking MS Entourage database files (or proprietary data formats for fun and profit)

Some time ago I found myself, for reasons known to some but
provacatively deffered to disclosure at a later date, with a strong
hankering to access the contents of a Microsoft Entourage database file.
Microsoft Entourage is, as you might suspect, a Microsoft product for OS
X, roughly analagous to Microsoft Outlook, serving as a personal
information manager, with email, contacts, calendar, to-do lists, and
related functions.  It maintains all related data in a single binary
blob datatabse for which no specification or public documentation is
available.

This wasn't just any database, but one which had been recovered from a
failed hard drive and apparently somewhat internally corrupted..  First
attempts at recovery, through Entourage's own database recovery
procedure, not surprisingly, failed.

Googling for recovery tools showed little in the way of anything useful,
though several sources suggested using binary editors to view content.
Doing so showed that there were large identifiable text blocks within
the database, including content that was clearly RFC 2822 email content.

Running 'strings' against the database produced output in which the
email and other content was more clearly evident, along with a number of
frequently occuring four-byte codes, similar to the following:

     1     5886 DELE
     2     5381 MLRC
     3     3070 popM
     4     2560 MLID
     5     2529 mesg
     6     2020 MSrc