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Posted 21 Mar 2003

SendTo mail recipient

, 31 Mar 2003
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Programmatically use the SendTo mail recipient shortcut


This article provides a code snippet in order to programmatically send one or more files to the mail recipient, mimicking the SendTo mail recipient shell extension. I have heard many people searching for this feature, and actually I thought that, as there doesn't seem to be such source code posted on the net, I could just as well post it.

Introducing the SendTo mail shortcut

You may skip this section if you are not interested in the r.e. technique.

The SendTo mail shortcut is a shell extension. See Mike Dunn's complete idiot guide for further info.

The trick is to find out that the SendTo mail recipient shortcut is actually essentially an empty file with .MAPIMAIL as (hidden) extension name. Then, by looking up file type association in the registry (HKCR\.MAPIMAIL), it's straight forward to figure out that it is targeting a COM object with clsid = {9E56BE60-C50F-11CF-9A2C-00A0C90A90CE}. This object is sendmail.dll, a COM helper which takes advantage of either Outlook Express or Outlook to send e-mail file attachments. Next, looking up this CLSID in OLE View clearly showed that the sendmail COM component also implements the IDropTarget, IShellExtInit and IPersistFile interfaces, just like any drop handler.

Ok, basically I need to prepare a bag with dropped filenames, make sure they can be retrieved by implementing the IDataObject interface, a simple communication interface, and then mimic a standard drag and drop sequence, with two check points : DragEnter(IDataObject*) and Drop(IDataObject*).

One of the interesting points is to start implementing the IDataObject interface starting with contract, i.e. the methods it is supposed to expose. And then cowardly insert a breakpoint into any default method implementation only to get to know whether it's called or not, and in what order.

If you are interested in mimicking other SendTo shortcuts, don't hesitate to check out this registry key: HKLM\Software\Microsoft\Windows\CurrentVersion\Shell Extensions\Approved.

IDataObject implementation

The following code implements the IDataObject interface. In fact, only a few methods are required to be implemented. Those are, in order:

  • EnumFormatEtc(), called by the sendmail helper to know what content formats the IDataObject is holding
  • IEnumFORMATETC::Next(),Reset(), called to list all formats. We are expected to let the sendmail helper know that we do hold the CF_HDROP clipboard format (standard used for file drag-and-drop support), even if in fact we are not using the clipboard at all.
  • GetData(), called to actually get the list of files we are willing to send.

Because on Windows file drag-and-drop operations rely on the CF_HDROP / DROPFILES structure, we simply prepare such a structure to play with. Here is the code :

#include <windows.h>
#include <ole2.h> // IDataObject
#include <shlobj.h> // DROPFILES
#include <tchar.h> // TCHAR

class CDataObject : public IDataObject, IEnumFORMATETC
  // Members
  BOOL m_bReset;
  LPTSTR m_szFiles;
  int m_nLen;

    // Constructor
  CDataObject(LPTSTR szFiles)

    if (!szFiles)
      m_szFiles = NULL;

    // replace \n chars with \0 chars
    m_nLen = _tcslen(szFiles)+1;
    m_szFiles = new TCHAR[m_nLen];
    memcpy(m_szFiles, szFiles, m_nLen * sizeof(TCHAR));

    LPTSTR szTmp = m_szFiles;
    while ( szTmp=_tcschr(szTmp,'\n') )
      *szTmp++ = '\0';


  virtual ~CDataObject()
    delete [] m_szFiles;

  HRESULT __stdcall QueryInterface(REFIID iid, void** ppvObject)
    *ppvObject = (IDataObject*) this;
    return S_OK;

  ULONG __stdcall AddRef()
    return 1;
  ULONG __stdcall Release()
    return 0;

  // IDataObject implementation
  HRESULT __stdcall GetData(FORMATETC* pFormatetc, STGMEDIUM* pmedium)
    if (pFormatetc->cfFormat != CF_HDROP  || !pmedium)
      return S_FALSE;

    if (!m_szFiles)
      return S_FALSE; // make sure to set the files before

    pmedium->tymed = TYMED_HGLOBAL;

    // set DROPFILES structure
    HGLOBAL hglbCopy = ::GlobalAlloc(GMEM_MOVEABLE, 
                 sizeof(DROPFILES) + (m_nLen + 2) * sizeof(TCHAR)); 
    LPDROPFILES pDropFiles = (LPDROPFILES) ::GlobalLock(hglbCopy);
    pDropFiles->pFiles = sizeof(DROPFILES);
    pDropFiles->pt.x = pDropFiles->pt.y = 0;
    pDropFiles->fNC = TRUE;
    pDropFiles->fWide = FALSE; // ANSI charset
    LPTSTR lptstrCopy = (LPTSTR) pDropFiles;
    lptstrCopy += pDropFiles->pFiles;
    memcpy(lptstrCopy, m_szFiles, m_nLen * sizeof(TCHAR)); 
    lptstrCopy[m_nLen] =  '\0';    // null character 
    lptstrCopy[m_nLen+1] = '\0';    // null character 

    pmedium->hGlobal = hglbCopy;
    pmedium->pUnkForRelease = NULL;

    return S_OK;

  HRESULT __stdcall GetDataHere(FORMATETC* pFormatetc, STGMEDIUM* pmedium)
    return S_OK;

  HRESULT __stdcall QueryGetData(FORMATETC* pFormatetc)
    return S_OK;

  HRESULT __stdcall GetCanonicalFormatEtc(FORMATETC* pFormatetcIn, 
                                          FORMATETC* pFormatetcOut)
    return S_OK;

  HRESULT __stdcall SetData(FORMATETC* pFormatetc, 
                   STGMEDIUM* pmedium, BOOL fRelease)
    return S_OK;

  HRESULT __stdcall EnumFormatEtc(DWORD dwDirection, 
                        IEnumFORMATETC** ppenumFormatetc)
    if (dwDirection==DATADIR_GET)
      *ppenumFormatetc = this;
      return S_OK;
      return S_FALSE;

  HRESULT __stdcall DAdvise(FORMATETC* pFormatetc, 
                            DWORD advf, 
                            IAdviseSink* pAdvSink, 
                            DWORD* pdwConnection)
    return S_OK;

  HRESULT __stdcall DUnadvise(DWORD dwConnection)
    return S_OK;

  HRESULT __stdcall EnumDAdvise(IEnumSTATDATA** ppenumAdvise)
    return S_OK;

  // IEnumFORMATETC implementation
  HRESULT __stdcall Next( 
            /*[in]*/ ULONG celt,
            /*[out]*/ FORMATETC __RPC_FAR* rgelt,
            /*[out]*/ ULONG __RPC_FAR* pceltFetched)
    if (!m_bReset) return S_FALSE;

    m_bReset = FALSE;

    FORMATETC fmt;
    fmt.cfFormat = CF_HDROP;
    fmt.dwAspect = DVASPECT_CONTENT;
    fmt.lindex = -1;
    fmt.ptd = NULL;
    fmt.tymed = TYMED_HGLOBAL;
    *rgelt = fmt; // copy struct
    if (pceltFetched) *pceltFetched = 1;

    return S_OK;
  HRESULT __stdcall Skip(/*[in]*/ ULONG celt)
    return S_FALSE;
  HRESULT __stdcall Reset()
    m_bReset = TRUE;
    return S_OK;
  HRESULT __stdcall Clone( 
            /* [out] */ IEnumFORMATETC** ppenum)
    return S_OK;

Using it

And here is how to use it to send c:\346.jpg and c:\tmp\


CDataObject cdobj("c:\\346.jpg\nC:\\tmp\\");
IDataObject *pDataObject = &cdobj;

IDropTarget *pDropTarget = NULL;

// create an instance, and mimic drag-and-drop
hr = ::CoCreateInstance( CLSID_SendMail,
                       NULL, CLSCTX_ALL,
                       (void **)&pDropTarget);
if (SUCCEEDED(hr))
  POINTL pt = {0,0};
  DWORD dwEffect = 0;
  pDropTarget->DragEnter(pDataObject, MK_LBUTTON, pt, &dwEffect);
  pDropTarget->Drop(pDataObject, MK_LBUTTON, pt, &dwEffect);




To compile this code, you only need WIN32.

Why SendTo is better than the mailto trick

You could tell me that shell-executing a mailto URL is just as fine, and much simpler code in practice. Yes and no. Yes, it does so, and it can't be simpler since that's only one line of code (just remember to escape ASCII chars in the body with hex replacements of the form %0D, %20, ...).

No, it does not provide support for file attachment(s), which is why the SendTo shortcut comes handy. And there is more to it. The truth is that ::ShellExecute() cannot handle parameter strings over 2048 bytes, which means your e-mail body size cannot go beyond 2048 bytes. If you try to send a large e-mail, it will result in a GPF. At this point, you could replace ::ShellExecute with a well thought ::WinExec call, using the actual mailto command line declared in the registry and target the current e-mail client (for instance, "%ProgramFiles%\Outlook Express\msimn.exe" /mailurl:%1). But then the limitation is 32 KB. As a conclusion, there is no way to send e-mails larger than 32KB using the mailto protocol. The SendTo shortcut explained in this article is definitely the way to go !


  • First relaese -March 22, 2003.
  • Updated on April 1st, removal of the clipboard use (Chris Guzak).


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


About the Author

Addicted to reverse engineering. At work, I am developing business intelligence software in a team of smart people (independent software vendor).

Need a fast Excel generation component? Try xlsgen.

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Comments and Discussions

GeneralRe: Anyone got code that works on XP Pro Pin
johnnycrash24-Jul-03 7:57
memberjohnnycrash24-Jul-03 7:57 
GeneralRe: Anyone got code that works on XP Pro Pin
Caddy24-Jul-03 13:20
memberCaddy24-Jul-03 13:20 
GeneralRe: Anyone got code that works on XP Pro Pin
johnnycrash24-Jul-03 13:48
memberjohnnycrash24-Jul-03 13:48 
GeneralRe: Anyone got code that works on XP Pro Pin
Caddy24-Jul-03 15:34
memberCaddy24-Jul-03 15:34 
GeneralRe: Anyone got code that works on XP Pro Pin
johnnycrash24-Jul-03 21:44
memberjohnnycrash24-Jul-03 21:44 
GeneralRe: Anyone got code that works on XP Pro Pin
Caddy25-Jul-03 10:38
memberCaddy25-Jul-03 10:38 
GeneralRe: Anyone got code that works on XP Pro Pin
johnnycrash25-Jul-03 12:24
memberjohnnycrash25-Jul-03 12:24 
Generalvb6 dll available! Pin
johnnycrash17-Jul-03 14:56
memberjohnnycrash17-Jul-03 14:56 
Thanks to everyone in this forum, I was able to make a dll that can be called from vb6 (in case anyone cares). This sure was a pain in the butt, without this article and subsequent posts, I never would have figured this out. If someone can tell me where to put it on some ftp site, I would love to upload it (compiled dll with all sourceode). Until then here is the source, and you can email me if you want the dll.

My method is a modification of the base method that requires no extra classes (yeah!), helper functions or anything. In the original example, stephan had to create a IDataObject derived class. In solving the XP problem, fuchs showed how the shell already has IDataObjects for files that you can use.

I think it is easy to understand (for com). It has to be since I knew diddly about c++ com programming until today. If I did some stupid stuff please tell me. I only tested this a couple times, so it probably has a bug. I will fix the bugs as I am using this in a deliverable, and I will repost.

Tested on Outlook express and Outlook.

Anyway, here is all the code

vb code to call it. Throw this on a form with a button.

Option Explicit
Private Declare Function SendToDefaultEmail Lib "xmain32b.dll" (ByVal szPName$, ByVal szFFiles$) As Long

Private Sub Command1_Click()
' separate multiple files with "|"
' must put path with backslash, files with no paths
SendToDefaultEmail "c:\", "boot.ini|bootlog.txt"

End Sub

dll source code follows...
Use vc6 to make a simple win32 dll named xMain32b, and then replace stdafx.h and xmain32b.cpp with the below code, and add xmain32b.def.


// xMain32b.cpp : Defines the entry point for the DLL application.

#include "stdafx.h"

// this guy is global because outlook express flips out if you kill this before hitting the send button.
IDropTarget *_pDropTarget = NULL;

BOOL APIENTRY DllMain(HANDLE hModule, DWORD fReason, LPVOID lpReserved)

switch (fReason) {
OleInitialize (NULL);

// create an instance, and mimic drag-and-drop
hr = ::CoCreateInstance(INLINE_UUID( "9E56BE60-C50F-11CF-9A2C-00A0C90A90CE"),
NULL, CLSCTX_ALL,IID_IDropTarget, (void **)&_pDropTarget);
if (!SUCCEEDED(hr))
_pDropTarget = NULL;



if (_pDropTarget)

OleUninitialize ();
return TRUE;
launch default email client with one or more attachment files. All files must be in same dir.

szFFiles = null term string of one or more files, with files separated with "|", no trailing "|". This will get munged.
szPName = put path with backslash

1 file --> SendToDefaultEmail "c:\\", "boot.ini"
2 files --> SendToDefaultEmail "c:\\", "boot.ini|bootlog.txt"

DllExport LONG WINAPI SendToDefaultEmail(char *szPName, char *szFFiles)

int cFiles, cbFiles, ich;
char *szFName;
IDataObject *pDataObject;
HRESULT hr = 0;
wchar_t wzPName[MAX_PATH];
wchar_t wzFName[MAX_PATH];
LPSHELLFOLDER pDeskTopFolder,pFolder;
LPITEMIDLIST pIdlFolder,pIdlFile;
POINTL pt = {0,0};

if (!(cbFiles = strlen(szFFiles))) goto ExitFunc;
for (cFiles=1,ich=0 ; szFFiles[ich] ; ++ich)
if (szFFiles[ich] == '|')
if (!(apIdlFiles = (LPCITEMIDLIST*)calloc(cFiles,sizeof(LPCITEMIDLIST)))) {
hr = -2;
goto ExitFunc;

// get any IShellFolder - desktop is convenient
if ((hr = SHGetDesktopFolder(&pDeskTopFolder)) != 0) goto ExitFunc;
// use that to Get a pidl for the folder.
if ((hr = pDeskTopFolder->ParseDisplayName(NULL, 0, wzPName, NULL, &pIdlFolder, NULL)) != 0) goto ExitFunc;
// use that to Get the IShellfolder for the folder containing the files
if ((hr = pDeskTopFolder->BindToObject(pIdlFolder,NULL,IID_IShellFolder,(void**)&pFolder)) != 0) goto ExitFunc;
// use that to Get the pidl for each file.
for (cFiles=0,szFName = strtok(szFFiles,"|") ; szFName ; szFName = strtok(NULL,"|")) {
if ((hr = pFolder->ParseDisplayName(NULL, 0, wzFName, NULL, &pIdlFile, NULL)) != 0) goto ExitFunc;
apIdlFiles[cFiles++] = pIdlFile;
// get the IDAtaObject for all the files.
if ((hr = pFolder->GetUIObjectOf(NULL,cFiles,apIdlFiles,IID_IDataObject,NULL,(void**)&pDataObject)) != 0) goto ExitFunc;
// serve up the drag and drop - our pDataObject onto _pDropTarget, the .mapimail drop target
if ((hr = _pDropTarget->DragEnter(pDataObject, MK_LBUTTON, pt, &dwEffect)) != 0) goto ExitFunc;
if (!dwEffect) {
hr = -1;
goto ExitFunc;
if ((hr = _pDropTarget->Drop(pDataObject, MK_LBUTTON, pt, &dwEffect)) != 0) goto ExitFunc;


if (apIdlFiles) free(apIdlFiles);
return hr;


DESCRIPTION "Implements usefull functions for openscan programs"


SendToDefaultEmail @1


// stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently, but
// are changed infrequently

#if !defined(AFX_STDAFX_H__F63181D9_FBE8_4BD0_8835_5EEC2FD181BB__INCLUDED_)
#define AFX_STDAFX_H__F63181D9_FBE8_4BD0_8835_5EEC2FD181BB__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

// Insert your headers here
#define WIN32_LEAN_AND_MEAN // Exclude rarely-used stuff from Windows headers

#include <windows.h>

// TODO: reference additional headers your program requires here
#include <ole2.h> // IDataObject
#include <shlobj.h> // DROPFILES
#include <tchar.h> // TCHAR

#define DllExport __declspec( dllexport )
extern "C" {
DllExport LONG WINAPI SendToDefaultEmail(char *szPFiles, char *szFFiles);

#define INLINE_UUID(x) __uuidof(struct __declspec(uuid(x)))

// Microsoft Visual C++ will insert additional declarations immediately before the previous line.

#endif // !defined(AFX_STDAFX_H__F63181D9_FBE8_4BD0_8835_5EEC2FD181BB__INCLUDED_)
GeneralRe: vb6 dll available! Pin
johnnycrash17-Jul-03 14:58
memberjohnnycrash17-Jul-03 14:58 
Generalworks for outlook, outlook express, eudora, but not calypso - is there a way to make it work for .lnk files? Pin
johnnycrash18-Jul-03 12:53
memberjohnnycrash18-Jul-03 12:53 
GeneralSend To Anything! Dll that can be called from vb6, and c++ source code Pin
johnnycrash18-Jul-03 17:15
memberjohnnycrash18-Jul-03 17:15 
GeneralRe: Send To Anything! Dll that can be called from vb6, and c++ source code Pin
Larry Hunt18-Jul-03 20:07
sussLarry Hunt18-Jul-03 20:07 
GeneralRe: Send To Anything! Dll that can be called from vb6, and c++ source code Pin
WayneHough12-Jul-06 9:06
memberWayneHough12-Jul-06 9:06 
GeneralRe: vb6 dll available! Pin
Carl03918-Jul-03 13:06
memberCarl03918-Jul-03 13:06 
GeneralRe: vb6 dll available! Pin
Anonymous21-Nov-03 6:20
sussAnonymous21-Nov-03 6:20 
GeneralRe: vb6 dll available! Pin
Dasith24-Nov-03 21:53
sussDasith24-Nov-03 21:53 
GeneralRe: vb6 dll available! Pin
Dasith24-Nov-03 21:53
sussDasith24-Nov-03 21:53 
GeneralRe: vb6 dll available! Pin
amanda_hua@hotmail.com3-Dec-03 14:00
memberamanda_hua@hotmail.com3-Dec-03 14:00 
GeneralThank you Pin
Larry Hunt25-Jun-03 9:22
sussLarry Hunt25-Jun-03 9:22 
GeneralRe: Thank you Pin
Martin Fuchs28-Jun-03 11:00
memberMartin Fuchs28-Jun-03 11:00 
GeneralRe: Thank you Pin
Martin Fuchs14-Jul-03 12:57
memberMartin Fuchs14-Jul-03 12:57 
GeneralRe: Thank you Pin
johnnycrash17-Jul-03 5:47
memberjohnnycrash17-Jul-03 5:47 
GeneralWindows XP Pin
Martin Fuchs17-Jul-03 22:54
memberMartin Fuchs17-Jul-03 22:54 
GeneralRe: Windows XP Pin
johnnycrash18-Jul-03 6:50
memberjohnnycrash18-Jul-03 6:50 
Generaldefault email address Pin
agd01119-Jun-03 10:55
memberagd01119-Jun-03 10:55 

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