How can I avoid Outlook's security warning on a .ics file?

Question

Hi all; I am creating a .ics file using iCal.Net. The file is correct and works. But when I go to open it, I'm using Outlook on Windows, I get:

But I get invites all the time in Outlook that I accept without this warning. So I looked on meetup.com and what it has for adding to the calendar is:

So, do I need to create 4 different calendar files so users can then select the appropriate one? Or is there a way to create a .ics that all the calendar apps accept without a security warning? thanks - dave

Answer 1

Hi @David Thielen

Welcome to our forum!

According to your description, the security warning you receive when you open an .ics file is due to a recent security update for the Outlook desktop. This is protection against the Microsoft Outlook information leak vulnerability.

You can disable by following the methods provided in this document: Outlook prompts security notice opening .ICS files after installing protections for Microsoft Outlook Information Disclosure Vulnerability released: Dec 12, 2023 - Microsoft Support.

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Answer 2

Outlook uses the vCalendar file format for invitations, but some other calendars such as Gmail use the iCalendar or iCal format. You can forward a single invitation in the iCal format from Outlook, or you can change the settings in Outlook to send multiple invitations in the iCal format. Alternatively, you can create a meeting template in Outlook and save it as an Outlook Template (*.oft) file. This way, you can reuse the template for future invitations without typing the same information again. To open a template, you need to go to New Items > More Items > Choose Form and select User Templates in File System.