Int 21 Fn 5F4D  u - LAN Manager Enhanced DOS - Dosmakemailslot             [N]

   AX = 5F4Dh
   BX = message size
   CX = mailslot size (must be bigger than message size by at least 1)
              (minimum 1000h, maximum FFF6h)
              (buffer must be 9 bytes bigger than this)
   DS:SI -> name
   ES:DI -> memory buffer

Return: CF clear if successful
       AX = handle
   CF set on error
       AX = error code

See Also: AX=5F4Eh,AX=5F4Fh,AX=5F50h,AX=5F51h