How To: Respond to an Outlook email programmatically

Several Outlook item types provide the Forward, Reply and ReplyAll methods. The table below lists the item types providing these methods as well as the item types that the methods return.

Let’s see how to use the information above to respond to a MailItem. In the code below, MailItem.Display is used for a demo; you can also call MailItem.Send.

The simplest way

Here’s one of the options of creating a reply to an email:

Imports System.Runtime.InteropServices
 Imports Outlook = Microsoft.Office.Interop.Outlook
 ...
 Private Sub Reply(mailItem As Outlook._MailItem)
     Dim response As Outlook._MailItem = mailItem.Reply()
     response.Display()
     Marshal.ReleaseComObject(response)
 End Sub

using System.Runtime.InteropServices;
 using Outlook = Microsoft.Office.Interop.Outlook;
 ...
 private void Reply(Outlook._MailItem mailItem)
 {
     Outlook._MailItem response = mailItem.Reply();
     response.Display(Type.Missing);
     Marshal.ReleaseComObject(response);
 }

The method above gets a response mail item from MailItem.Reply, calls MailItem.Display to show the response and releases the COM object by calling Marshal.ReleaseComObject. The need for the last call is discussed in When to release COM objects in a managed COM add-in?

Problems & solutions

There are problems with the mail items that are created using Forward, Reply and ReplyAll methods. Say, when using these methods, the “Close original message on reply or forward” flag doesn’t apply. This seems to be rational, however. If you need to emulate this behavior, you’ll need to read the value called CloseOrig in the following registry key:

HKEY_CURRENT_USER\Software\Microsoft\Office\{version}.0\Outlook\Preferences.

We were also reported about Outlook 2003-2007 ignoring the options “Mark my comments with” and “Ignore original message text in reply or forward”.

Actions

In fact, the Forward, Reply and ReplyAll methods perform the corresponding actions basing on the user settings. The settings can be found in these locations in Outlook:

• Outlook 2010, on the File tab you choose Options and, on the Mail tab, see Replies and Forwards
• In Outlook 2007, 2003, 2002 and 2000, from the Tools menu you choose Options, click the Preferences tab and click E-mail Options

You can overwrite the settings to create a response in a non-default style. You do this as follows:

Imports System.Runtime.InteropServices
Imports Outlook = Microsoft.Office.Interop.Outlook
...
Private Sub Reply(mailItem As Outlook._MailItem)
    Dim actions As Outlook.Actions = mailItem.Actions
    Dim action As Outlook.Action = actions("Reply")
    Marshal.ReleaseComObject(actions)
    action.ReplyStyle = Outlook.OlActionReplyStyle.olIncludeOriginalText
    Dim response As Outlook._MailItem = CType(action.Execute(), Outlook.MailItem)
    Marshal.ReleaseComObject(action)
    response.Display()
    Marshal.ReleaseComObject(response)
End Sub

using System.Runtime.InteropServices;
using Outlook = Microsoft.Office.Interop.Outlook;
...
private void Reply(Outlook._MailItem mailItem)
{
    Outlook.Actions actions = mailItem.Actions;
    Outlook.Action action = actions["Reply"];
    Marshal.ReleaseComObject(actions);
    action.ReplyStyle = Outlook.OlActionReplyStyle.olIncludeOriginalText;
    Outlook._MailItem response = action.Execute() as Outlook.MailItem;
    Marshal.ReleaseComObject(action);
    response.Display();
    Marshal.ReleaseComObject(response);
}

Problems & solutions

Note however that running the code above modifies the source mail item. This produces the message box “The properties of the message %SUBJECT% have been changed. Do you want to save changes to this message?” when you close the Inspector window or, if the item wasn’t opened, when you close Outlook.

To prevent the message from occurring, your code should restore the settings of the action and save the item (MailItem.Save) before the user has a chance to close the inspector. Or, in the case of inspector window, you may choose to close the inspector discarding the changes (Inspector.Close).

Good luck!