function sendMail( const TargetName, TargetAddr,
                         SenderName, SenderAddr,
                         MsgSubject, MsgContent,
                         Attachment : String;
                         PreviewMsg : Boolean = TRUE ) : Integer;
var
  msg       : TMapiMessage;    // Pointer to the message itself
  mrdSender,                   // Who's sending it?
  mrdTarget : TMapiRecipDesc;  // Who's going to get it?
  mfdAttach : TMapiFileDesc;   // The attached file.
  liFlags   : Longint;         // Flags for MAPI.
  strError  : String;          // Holds MAPI error results;
begin
 result := 0;
 liFlags := 0;
 fillChar( msg, sizeOf( msg ), 0 );
 with msg do
 begin

   if TargetAddr = '' then
      raise tMailFileException.createFmt( ERROR,
         [ 'Target email address not specified' ] )
   else begin
      if TargetName = '' then
         mrdTarget.lpszName := pChar( TargetAddr )
      else
         mrdTarget.lpszName := pChar( TargetName );
      mrdTarget.ulRecipClass := MAPI_TO;
      mrdTarget.lpszAddress := pChar( TargetAddr );
      mrdTarget.ulReserved := 0;
      mrdTarget.ulEIDSize := 0;
      mrdTarget.lpEntryID := NIL;
      nRecipCount := 1;
      lpRecips := @mrdTarget;

   end;

   if SenderAddr = '' then
      raise tMailFileException.createFmt( ERROR,
         [ 'Sender email address not specified' ] )
   else begin
      if SenderName = '' then
         mrdSender.lpszName := pChar( SenderAddr )
      else
         mrdSender.lpszName := pChar( SenderName );
      mrdSender.ulRecipClass := MAPI_ORIG;
      mrdSender.lpszAddress := pChar( 'SMTP:' + SenderAddr );
      mrdSender.ulReserved := 0;
      mrdSender.ulEIDSize := 0;
      mrdSender.lpEntryID := NIL;
      lpOriginator := @mrdSender;
   end;

   if MsgSubject = '' then
      lpszSubject := ''
   else
      lpszSubject := pChar( MsgSubject );

   if ( MsgContent = '' ) AND ( Attachment = '' ) then
      raise tMailFileException.createFmt( ERROR,
         [ 'Tried to send an empty message (no content or attachment)' ] )
   else begin
      if MsgContent = '' then
         lpszNoteText := 'Please see the attached file.'
      else
         lpszNoteText := pChar( MsgContent );

      if Attachment = '' then begin
         nFileCount := 0;
         lpFiles := NIL;
      end else begin
         fillChar( mfdAttach, sizeOf( mfdAttach ), 0 );
         mfdAttach.nPosition := cardinal( $FFFFFFFF );
         mfdAttach.lpszPathName := pChar( Attachment );
         nFileCount := 1;
         lpFiles := @mfdAttach;
      end;
   end; // with

   if previewMsg then liFlags := MAPI_DIALOG;

   result := mapiSendMail( 0, application.Handle, msg, liFlags, 0 );

   if result <> 0 then
      raise tMailFileException.createFmt( ERROR,
         [ 'MAPI triggered an error ('
           + getMAPIError( result ) + ')' ] );
  end;

end;

uses mapimail;
// ...other stuff
procedure TForm1.btnSendMailClick(Sender: TObject);
begin

   sendMail( edtTargetName.Text, edtTargetAddr.Text,
             edtSenderName.Text, edtSenderAddr.Text,
             edtMsgSubject.Text, mmoMsgContent.Text,
             edtAttachment.Text, chkPreviewMsg.Checked );

end;