The Content-Type table defines how an attachment is read, and
 optionally,  how its output is converted when extracted with the
 X-FDL=file option. It is constructed from program built-in types
 and is read from the optional MIME$MAILCAP.DAT configuration files
 (if they exist).

   SYS$MANAGER:MIME$MAILCAP.DAT

   SYS$LOGIN:MIME$MAILCAP.DAT

 System-wide Content-Types are specified by the file
 SYS$MANAGER:MIME$MAILCAP.DAT and can be supplemented with
 additional entries found in the SYS$LOGIN:MIME$MAILCAP.DAT file.
 These files are not created by default for customization on a per
 system/site basis. The MIME$MAILCAP.DAT file follows the general
 format of (Request for Comments) RFC 1524.

   TYPE/SUBTYPE VIEW_COMMAND

 The Content-Type table is constructed beginning with the built-in
 types, then adding the system definitions from the system manager's
 MIME$MAILCAP.DAT file, and ending with data from the user's
 default login directory MIME$MAILCAP.DAT file.

 The entries are displayed in order of the most recently defined
 (LIFO) entries. In the case of duplicate entries, the first entry
 is used. This allows a user to customize their own environment while
 the system manager defines a default system or site environment
 for all users.

 Note that by default, only the minimal ASCII types and subtypes are
 defined. This allows customizing MIME to the system, and for security
 reasons, allows a regulated site environment.

 Consider the effect of a malicious user mailing a harmful image
 (.EXE) file that is executed upon being read with the OpenVMS MIME
 utility. RFC 2046 lists certain security considerations that should
 be noted, such as PostScript files that include PostScript operators
 such as "deletefile" and others that can be used in a malicious
 manner.

 For more information, see Example_MIME$MAILCAP.DAT help section.