Here's an IConvertSession proxy for C#:
using Microsoft.Office.Interop.Outlook;
using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Runtime.InteropServices.ComTypes;
namespace Exchange.Export.MAPIMessageConverter
{
internal class MAPIMethods
{
[Flags]
public enum MAPITOMIMEFLAGS
{
CCSF_SMTP = 0x0002,
CCSF_NOHEADERS = 0x0004,
CCSF_USE_TNEF = 0x0010,
CCSF_INCLUDE_BCC = 0x0020,
CCSF_8BITHEADERS = 0x0040,
CCSF_USE_RTF = 0x0080,
CCSF_PLAIN_TEXT_ONLY = 0x1000,
CCSF_NO_MSGID = 0x4000,
}
[Flags]
public enum CLSCTX
{
CLSCTX_INPROC_SERVER = 0x1,
CLSCTX_INPROC_HANDLER = 0x2,
CLSCTX_LOCAL_SERVER = 0x4,
CLSCTX_REMOTE_SERVER = 0x10,
CLSCTX_INPROC = CLSCTX_INPROC_SERVER | CLSCTX_INPROC_HANDLER,
CLSCTX_SERVER = CLSCTX_INPROC_SERVER | CLSCTX_LOCAL_SERVER | CLSCTX_REMOTE_SERVER,
CLSCTX_ALL = CLSCTX_SERVER | CLSCTX_INPROC_HANDLER
}
public static Guid CLSID_IConverterSession = new Guid("{4e3a7680-b77a-11d0-9da5-00c04fd65685}");
public static Guid IID_IConverterSession = new Guid("{4b401570-b77b-11d0-9da5-00c04fd65685}");
public enum ENCODINGTYPE
{
IET_BINARY = 0,
IET_BASE64 = 1,
IET_UUENCODE = 2,
IET_QP = 3,
IET_7BIT = 4,
IET_8BIT = 5,
IET_INETCSET = 6,
IET_UNICODE = 7,
IET_RFC1522 = 8,
IET_ENCODED = 9,
IET_CURRENT = 10,
IET_UNKNOWN = 11,
IET_BINHEX40 = 12,
IET_LAST = 13
}
public enum MIMESAVETYPE
{
SAVE_RFC822 = 0,
SAVE_RFC1521 = 1
}
[ComVisible(false)]
[ComImport()]
[Guid("00020307-0000-0000-C000-000000000046")]
[InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
public interface IMessage
{
}
[ComImport]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
[Guid("4b401570-b77b-11d0-9da5-00c04fd65685")]
public interface IConverterSession
{
[PreserveSig]
int Placeholder0();
[PreserveSig]
uint SetEncoding(
[In, MarshalAs(UnmanagedType.I4)] ENCODINGTYPE DispId
);
[PreserveSig]
int Placeholder1();
[PreserveSig]
uint MIMEToMAPI(
[In, MarshalAs(UnmanagedType.Interface)]
Stream pstm,
[Out, MarshalAs(UnmanagedType.Interface)]
MailItem pmsg,
object pszSrcSrv,
uint ulFlags
);
[PreserveSig]
uint MAPIToMIMEStm(
[In, MarshalAs(UnmanagedType.Interface)]
IMessage pmsg,
[Out, MarshalAs(UnmanagedType.Interface)]
IStream pstm,
MAPITOMIMEFLAGS ulFlags
);
[PreserveSig]
int Placeholder2();
[PreserveSig]
int Placeholder3();
[PreserveSig]
int Placeholder4();
[PreserveSig]
int SetTextWrapping(
bool fWrapText,
uint ulWrapWidth
);
[PreserveSig]
uint SetSaveFormat(
[In, MarshalAs(UnmanagedType.I4)]
MIMESAVETYPE mstSaveFormat
);
[PreserveSig]
int Placeholder5();
[PreserveSig]
int Placeholder6();
}
}
}
Using it:
private Stream GetEmlStream(Outlook.MailItem mail)
{
Type converter = Type.GetTypeFromCLSID(MAPIMethods.CLSID_IConverterSession);
object obj = Activator.CreateInstance(converter);
MAPIMethods.IConverterSession session = (MAPIMethods.IConverterSession)obj;
if (session != null)
{
uint hr = session.SetEncoding(MAPIMethods.ENCODINGTYPE.IET_QP);
hr = session.SetSaveFormat(MAPIMethods.MIMESAVETYPE.SAVE_RFC822);
var stream = new ComMemoryStream();
hr = session.MAPIToMIMEStm((MAPIMethods.IMessage)mail.MAPIOBJECT, stream, MAPIMethods.MAPITOMIMEFLAGS.CCSF_SMTP);
if (hr != 0)
throw new ArgumentException(There are some invalid COM arguments");
stream.Position = 0;
return stream;
}
return null;
}
ComMemoryStream: https://stackoverflow.com/a/6602066/2532356
Other fonts:
http://www.pcreview.co.uk/threads/iconvertersession-in-c.3716714/
http://www.microsoft-questions.com/microsoft/Plaform-SDK-Mapi/31018989/mimetomapi-and-mapitomimestm-method-take-a-pointer-to-an-imessage-extended.aspx