INT 92 - Da Vinci eMail Dispatcher - "NetWrite"
        AX = E108h
        BX = 0004h
        CX:DX -> parameter block (see below)
Return: AX = amount written
Note:   this function is used to write transactions to the dispatcher.
          The command block is written first and then another call is used
          to write the associated data.

Format of parameter block:
Offset  Size    Description
 00h    WORD    buffer count
 02h    WORD    segment of command buffer
 04h    WORD    offset of command buffer
 06h    WORD    handle from NetOpen

Format of command buffer:
Offset  Size    Description
 00h    BYTE    command
                21h '!' Protocol commands for remote control
                41h 'A' Authorization protocol element
                42h 'B' Return(back) routing information
                    Associated data is the From: username
                43h 'C' Carbon Copy list
                    Associated data is a comma delimitted list of usernames
                44h 'D' Distribution list
                    Associated data is a comma delimitted list of usernames
                45h 'E' Mail end marker
                    No associated data
                48h 'H' Mail message header
                    Associated data is a message header buffer
                4Dh 'M' Mail message
                    Associated data is the body of the message
                4Fh 'O' Object
                50h 'P' Paperclip attachment
                52h 'R' Routing information
                    Associated data is the To: username
                53h 'S' Subject
                    Associated data is the subject of the message
                54h 'T' Trail of Reply/Forwards
 01h    BYTE    subcommand
 02h    DWORD   length of associated data

Format of message header buffer:
Offset  Size    Description
 00h 30 BYTEs   subject line
 1Eh 24 BYTEs   To
 36h 24 BYTEs   From
 4Eh    DWORD   Time
                BYTE    0
                BYTE    hour
                BYTE    minute
                BYTE    second
 52h    DWORD   Date
                BYTE    0
                BYTE    year
                BYTE    month
                BYTE    day
 56h    DWORD   serial number (0L)
 5Ah    WORD    mail types
                bit 7   blind carbon copy
                bit 6   carbon copy
                bit 5   priority
                bit 4   confidential
                bit 3   certified
                bit 2   bulk
                bits 1-0 class (first, second, third, bulk)
 5Ch    WORD    special types (0)