c#之在 Outlook 加载项中以 MIME 格式 (*.eml) 保存邮件

我想编写一个小的 Outlook 插件 (C#)，它将选定的邮件 (MailItem) 以纯 MIME 格式 (.eml) 保存到磁盘。 MailItem.SaveAs() 方法只允许以 .msg 格式保存。 是否有任何其他(简单)方法可以将邮件保存为 eml 格式？我想保留原始邮件的所有详细信息。

我读过一些有关 Outlook Web 服务的内容。也许我可以在 exchange 服务器上搜索当前在 outlook 中选择的邮件并从 exchange 再次接收它并将其保存为 .eml？选择此选项需要什么？

是否可以通过简单的方式将保存的 .msg 转换为 .eml(保留所有详细信息、标题等)？

我希望有人能帮助我解决这个问题，因为我已经花了几个小时寻找解决方案但没有任何结果。

请您参考如下方法:

这是 C# 的 IConvertSession 代理:

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(); 
        } 
    } 
} 

使用它:

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

其他字体:

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