Convert EML to MSG c# Using EWS

Question

I need help with converting EML to MSG, using the Exchange web service (EWS) in a Outlook Web Add-In. When i create an EML file from the MimeContent (EmailMessage.MimeContent.Content), the file output looks bad, some tags are not convert currently. The files open good just from Windows mail app, but from Ooutlook(2016) looks bad.

I tried to find some solution from Microsoft and found this Independentsoft, a third party solution, and it is work great. the file looks good while the format is MSG. but it is to expansive licence solution for the customer (used 30 days demo). This is what i used and work well, and try to found something like this:

//1.This code use the EWS mimeContent(the message on bytes - eml format)
//2.Create Independentsoft message object 
//Independentsoft.Msg.Message constractor do the convert by
// making an msg object from an eml object.
//3. save the msg file.
Independentsoft.Email.Mime.Message mimeMessage = new Independentsoft.Email.Mime.Message(emailMessage.MimeContent.Content);
Independentsoft.Msg.Message msgMessage = Independentsoft.Msg.Message(mimeMessage);
using (MemoryStream memStream = new MemoryStream(emailMessage.MimeContent.Content.Length))
{
    Directory.CreateDirectory(TempMsgDirectory);    
    msgMessage.Save(TempMsgDirectory + "mail.msg", true);
}

Answer 1

I am not aware of any Outlook problems with displaying EML files. It uses the same EML parser used to parse incoming POP3/IMAP4 messages. Please post a specific EML file that Outlook does not display correctly.

As for converting EML files to MSG, you can also use Redemption (I am its author) and its RDOSession.CreateMessageFromMsgFIle and RDOMail.Import methods. Just keep in mind that it requires the MAPI system to be present to function properly, which means Outlook must be installed locally.

Off the top of my head:

RDOSession session = new RDOSession();
RDOMail msg = session.CreateMessageFromMsgFile(TempMsgDirectory + "mail.msg");
msg.Import(TempMsgDirectory + "YouEmlFile.eml", rdoSaveAsType.olRFC822);
msg.Save();

Also keep in mind that retrieving MIME content from Exchange might not be the best idea - you will lose all MAPI specific properties and will end up with a corrupted message if the original was in the RTF format (with or without embedded OLE objects). In that case, you can use ExportItems EWS operation. Its format is not documented, but it is very close to the MSG format, and you can convert it to MSG using code similar to that above, but specifying olFTS format instead of olRFC822.