Begins the actual sending of the message after the message has
    been constructed.
    Format
      MAIL$SEND_MESSAGE  context ,in_item_list ,out_item_list
1 – Returns
    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value
    Longword condition value. All utility routines return a condition
    value in R0. Condition values that can be returned by this
    routine are listed under Condition Values Returned.
2 – Arguments
 context
    OpenVMS usage:context
    type:         longword (unsigned)
    access:       modify
    mechanism:    by reference
    Send context information to be passed to send routines. The
    context argument is the address of a longword that contains send
    context information returned by MAIL$SEND_BEGIN.
 in_item_list
    OpenVMS usage:itmlst_3
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference
    Item list specifying options for the routine. The in_item_list
    argument is the address of a list of item descriptors, each of
    which specifies an option and provides the information needed to
    perform the operation.
    The item list is terminated by longword value of 0.
3 – Input Item Codes
 MAIL$_SEND_ERROR_ENTRY
    MAIL$_SEND_ERROR_ENTRY specifies the longword address of an entry
    point to process errors during a send operation. The descriptor
    of the recipient that failed, the address of the signal array,
    and the user-specified data are passed as input to the routine.
    Refer to the HP OpenVMS Programming Concepts Manual for more
    information about the signal array and its use by condition-
    handling routines.
 MAIL$_SEND_RECIP_FOLDER
    MAIL$_SEND_RECIP_FOLDER specifies the descriptor of a recipients
    folder name. If you do not specify the MAIL$_SEND_RECIP_FOLDER
    item code, the mail will be sent to the default NEWMAIL folder. A
    valid folder name can be 1 to 39 characters in length.
 MAIL$_SEND_SUCCESS_ENTRY
    MAIL$_SEND_SUCCESS_ENTRY specifies the longword address of an
    entry point to process successes during a send operation. The
    descriptor of the recipient that succeeded, the address of the
    signal array, and the user-specified data are passed as input
    to the routine. Refer to the HP OpenVMS Programming Concepts
    Manual for more information about the signal array and its use by
    condition-handling routines.
 MAIL$_SEND_USER_DATA
    MAIL$_SEND_USER_DATA specifies a longword that MAIL$SEND_MESSAGE
    passes to the SEND action routines.
 out_item_list
    OpenVMS usage:itmlst_3
    type:         longword
    access:       write only
    mechanism:    by reference
    Item list specifying the information you want the routine to
    return. The out_item_list argument is the address of a list of
    item descriptors, each of which describes an item of information.
    The list of item descriptors is terminated by longword value of
    0.
4 – Output Item Codes
None.
5 – Description
    The MAIL$SEND_MESSAGE routine sends a message built with the
    MAIL$SEND_ADD_BODYPART routine to every user on the address
    list. If you have not used MAIL$SEND_ADD_BODYPART to construct
    a message, MAIL$SEND_MESSAGE sends only a message header.
    If MAIL$SEND_MESSAGE encounters errors sending to an addressee,
    it calls the routine specified by MAIL$_SEND_ERROR_ENTRY.
    Otherwise, it calls the routine specified by MAIL$_SEND_SUCCESS_
    ENTRY.
    If either routine is not specified, MAIL$SEND_MESSAGE calls no
    other routines.
    If you specify the MAIL$_SEND_RECIP_FOLDER item code, the mail
    is placed in the specified folder. Otherwise, the mail is sent to
    the default NEWMAIL folder.
6 – Condition Values Returned
    MAIL$_INVITMCOD    The specified item code is invalid.
    MAIL$_INVITMLEN    The specified item length is invalid.
    MAIL$_MISREQITEM   The required item is missing.
    SS$_ACCVIO         Access violation.
    Any condition value returned by $CONNECT.