Outlook 365 for desktop add-in not working


i have converted a outlook 2010 addin project into outlook 365(for desktop), after that when it reach below line

Private Sub ThisAddIn_Startup() Handles Me.Startup Try

    Dim Application As Microsoft.Office.Interop.Outlook.Application = New Microsoft.Office.Interop.Outlook.Application 'EXCEPTION LINE

then immediately throws exception as like below

{"Retrieving the COM class factory for component with CLSID {0006F03A-0000-0000-C000-000000000046} failed due to the following error: 8000ffff Catastrophic failure (Exception from HRESULT: 0x8000FFFF (E_UNEXPECTED))."}

I read the topic Why am I receiving exception from Office's Outlook library? but, in my case its not resolved the issue.

experts please advise me.

asked on Stack Overflow Mar 20, 2020 by Jey2331129

1 Answer


You are already inside outlook (ThisAddin class), so you do not need to create a new instance of the application. What you need is to get a pointer to the existing one.

I do not code in VB.Net but the C# equivalent would be:


I am assuming you want to mimic what is present in the code you are pointing to and want to send an email then I would write it like this:

public void Email_Send()
    O.MailItem message = this.Application.CreateItem(O.OlItemType.olMailItem);
    message.To = Receiver;
    message.CC = Sender;
    message.Subject = Subject;
    message.Body = "This is an automated message sent at " + DateTime.Now.ToString("HH:mm:ss") + " about " + Body_Topic + System.Environment.NewLine + Body_Content ;
answered on Stack Overflow May 11, 2020 by EPR

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