Reading an .eml (outlook email) file using c#

Question

I'm writing a service that cleans files by removing all malicious content. I'm using Interop Excel & Word api's like this:

Excel

    var excelApp = new Microsoft.Office.Interop.Excel.Application();
    excelApp.Visible = false;
    excelApp.AutomationSecurity = Microsoft.Office.Core.MsoAutomationSecurity.msoAutomationSecurityForceDisable;
    try
    {
        var workbook = excelApp.Workbooks.Open(fileToClean.InputFileName);

Word

    var wordApp = new Microsoft.Office.Interop.Word.Application
    {
        Visible = false,
        AutomationSecurity = Microsoft.Office.Core.MsoAutomationSecurity.msoAutomationSecurityForceDisable
    };

    try
    {
        var wordDoc = wordApp.Documents.Open(fileToClean.InputFileName, false, true);

I'm trying to find a similar way to open .eml Outlook files. I can't find any way of opening a .eml file using the Outlook Interop.

Dmitry Streblechenko · Answer 1 · 2022-05-03T18:17:55.033

EML file format is not native for Outlook - MSG format is (you can open an MSG file using Namespace.GetSharedItem). Even if Outlook will be happy to open an EML file for you if you double click on it in Windows Explorer.

To read an EML file, you would need to either parse it explicitly in your code, or to use one of numerous MIME processing libraries. If using Redemption (I am its author) is an option, you can create a temporary MSG file and import EML file into it.

The following code will create an MSG file and import an EML file into it using Redemption (RDOSession object):

  set Session = CreateObject("Redemption.RDOSession")
  Session.MAPIOBJECT = outlookApp.Session.MAPIOBJECT
  set Msg = Session.CreateMessageFromMsgFile("C:\Temp\temp.msg")
  Msg.Import "C:\Temp\test.eml", 1024
  Msg.Save
  MsgBox Msg.Subject

You can then use the message (RDOMail) to access it various properties (Subject, Body, etc.)

Also keep in mind no Office app (Excel, Word, or Outlook) can be used from a Windows service (such as IIS).

thanks Dmitry, I will give this a try. To get past the office app not allowed to run as a service i created an exe an it's running on a server. It monitors a specific folder, when ever a file is dumped in that folder it picks it up, cleans it and saves it in another folder, so the calling system gets the cleaned file from the output folder.. — Andre Grobler, Nov 20 '17 at 09:05
But that means there must always be an interactive user logged in, right? — Dmitry Streblechenko, Nov 20 '17 at 15:39

score 0 · Answer 2 · answered Nov 27 '17 at 12:56

Thanks to Dmitry I managed to find a solution. I ended up using Independentsoft.Msg nuget package. The code is here:

Message message = new Message(fileToClean.InputFileName);
var attachmentList = new List<Attachment>();

// First check all attachments, and add the clean ones to the attachment list
foreach (BodyPart bodyPart in message.BodyParts)
{
    if ((bodyPart.ContentDisposition != null) &&
        (bodyPart.ContentDisposition.Type == ContentDispositionType.Attachment))
    {
        foreach (Attachment attachment in message.GetAttachments())
        {
            if (attachment.GetFileName() == bodyPart.ContentDisposition.Parameters[0].Value)
            {
                if (IsClean(attachment, fileToClean))
                {
                    attachmentList.Add(attachment);
                }
                break;
            }
        }
    }
}

// Remove all attachements
message.BodyParts.RemoveAll(bp =>
                       (bp.ContentDisposition != null) &&
                       (bp.ContentDisposition.Type == 
ContentDispositionType.Attachment));

// Attach Cleaned attachments
foreach (Attachment attachment in attachmentList)
{
    message.BodyParts.Add(new BodyPart(attachment));
}

Reading an .eml (outlook email) file using c#

2 Answers2