Question

We’ve written an Outlook plugin using Add-in-Express. Code:

private void CreateShowMessageUsingCreateItem(Outlook._Application OutlookApp) 
{ 
    Outlook.MailItem mail = null; 
    try 
    { 
        mail = OutlookApp.CreateItem(Outlook.OlItemType.olMailItem) as Outlook.MailItem; 
        mail.Save(); 
        mail.Display(false); 
    } 
    catch (Exception ex) 
    { 
        System.Windows.Forms.MessageBox.Show(ex.Message); 
    } 
    finally 
    { 
        if (mail != null) Marshal.ReleaseComObject(mail); 
    } 
} 

Works when Outlook is connected to Exchange. Fails when
Outlook is connected to Office365. Error:

Exception: System.Runtime.InteropServices.COMException (0x80004005): The operation failed.
   at Microsoft.Office.Interop.Outlook.ApplicationClass.CreateItem(OlItemType ItemType)
   at DocuSignInk.DSToolbox.ShowResponse(MailItem senderEmail) in C:\docusign_source\Ink_Outlook\DocuSignInk\DSToolbox.cs:line 540

Some research indicates that you need to release your objects
when making these calls in a loop. But I’m not in a loop. I
can’t even get one call to work, so I don’t get to the point
where I can release anything.

Testing with Wireshark and Charles indicates that the problem is
in the client. I was trying to see if there is a more detailed
error coming from the server, but there’s no traffic to the server
at all.

A quick Python script works from the command line.

import win32com.client

outlook = win32com.client.Dispatch('Outlook.Application')
mail = outlook.CreateItem(win32com.client.constants.olMailItem)
mail.Save()
mail.Display(False)

So it must be something in the client. I’m guessing maybe thread-related?

Answer 1

This can happen if you haven’t activated Microsoft Office (which includes Outlook).

Short, test add-ins can work if they run right away before the activation check happens.
Once the activation check happens the API calls will fail.