Where was this information obtained? The session notes were created by looking
through the VMS V5.1-1 micro-fiche. Since this is an undocumented interface,
DEC is free to change it at any time (and, in fact, has made slight changes
to it between 5.0, 5.1 and 5.2). These session notes should provide a guideline,
but you may need to look through the header files and note changes, as well
as check the micro-fiche.

Facility: MAILSHR	V5.0    | V5.1    | V5.2   		
	FILEFRONT.LIS	328 I05 | 328 I05 | 717 K13		
	MSGFRONT.LIS	331 L06 | 702 J11 | 720 L13		
	SENDFRONT.LIS	334 B11 | 704 C09 | 724 D03		
	USERFRONT.LIS	336 E12 | 336 E12 | 726 C05		

Facility: VMSLIB
	$MAILDEF.SDL	635 G01            1059 J15

Each of these modules start with a list of what items are 'boolean',
followed by a list of the sizes of all the other items. A negative size
indicates the maximum size for a variable length item. For example,
in FILEFRONT.LIS (page 328 - L5), look for MAILFILE_BOOLEAN_ITEM_LIST,
and MAILFILE_REQUIRED_ITEM_LIST.

Following this, you need to search for each individual mail routine, for
example, the first routine of interest in FILEFRONT.LIS, is
MAIL$MAILFILE_BEGIN (on 328 - N6). At the beginning of each of these routines
is a list of what items are required, and which are allowed. Look
for 4 arrays, with names like REQUIRED_MAILFILE_BEGIN_INPUT,
REQUIRED_MAILFILE_BEGIN_OUTPUT, ALLOWED_MAILFILE_BEGIN_INPUT,
and ALLOWED_MAILFILE_BEGIN_OUTPUT. For example, for MAILFILE_BEGIN,
there are no required or allowed inputs, no required outputs,
and an allowed output of MAIL$_MAILFILE_MAIL_DIRECTORY.

Okay, so that's how you figure out the size of the data items, and which
routines allow which items. Well, what else is left? The header file,
MAILDEF (or $maildef), should be created automatically by most of the
compilers, be sure to reinstall your compilers when you upgrade the
operating system so that you have the latest version.

Most notable (perhaps only?) changes:
	The flags word changed, the bit that WAS "mail$v_del", became
"mail$v_dwmail", and the bit mail$v_sysmsg became mail$v_notrans. This
happened with VMS V5.1 (although no changes are included in the microfiche!).