Int 16 Fn 4504  - Shamrock Software EMail - Check For User Function Comma  [e]

   AX = 4504h
   DL = port number (01h = COM1)
   ES:BX -> 80-byte buffer for ASCIZ user input line

Return: AX = 4D00h if EMAIL installed on specified port
       DL = flags
       bit 0: user function supported (always set)
       bit 1: user entered user-function command word
       if DL bit 1 set,
       ES:BX buffer contains line entered by user which begins with
           the defined command word and has been converted to all
           caps

Note:  caller must process the returned commandline and invoke AX=4505h
     within five seconds with the result of that processing

See Also: AX=4503h,AX=4505h