Calendar Invites Don’t Work

Calendar Invites Don’t Work. A reader asks…

I use Outlook for email, calendar, & contact lists on my Windows 11 PC. Sometimes when I get an appointment invitation it shows up on my calendar automatically, and the email just has buttons to Accept, Tentative, or Decline. But sometimes what I get has a file attachment in it, and I when I try to open it, some other email app opens. Why does this happen, and how can I get that 2nd type of invitation to work right?

With different systems, the go-between method is for one system to send the other a file attachment that ends in “.ics”. That’s a plain-text file that stores calendar data in the iCalendar format.

The reason you get two different types of appointment emails is because not everybody uses the same email system or service. You use Outlook, another person may use Apple Mail, or Gmail, or any one of a number of systems that have an integrated calendar. The integration works fine when you’re both using the same system – so the first type you mention with the Accept, Tentative and Decline buttons is well integrated since you both use Outlook to manage your calendar appointments.

The reason your computer can’t recognize the file attachment for that 2nd type of invitation is most likely because your computer hasn’t registered the .ics file as belonging to Outlook. Windows uses a list of “default apps” that are registered to use different file types. For example, the .docx file type goes with Microsoft Word. But even though you’ve installed and use Outlook for your email, contacts and calendar, your computer needs to have Outlook registered to handle those .ics file types. Here’s how:

In Windows type “default apps” into the search box that’s at the bottom-left of your screen by the Windows start button, and then press your keyboard Enter key. That opens up a window to your Default Apps settings with a menu of settings on the left, and the Default Apps settings on the right. There are two boxes where you can set, one for file type or link type, and one for applications.

Click inside the box that has “Enter a file type or link type” and type “.ics” into the box. Directly underneath that box you’ll see whatever app Windows thinks should handle this type. Most likely it’s the standard Windows Mail app icon. Click that app icon to pop up a list where you can pick which application you want to use with those .ics files.

You’ll want to choose one of the Outlook icons from this list. Which one depends on which version of Outlook you’re using. Microsoft is pushing people to the “Outlook (new)” option, but many folks like myself prefer the classic Outlook interface. Once you’ve chosen the Outlook version you use, click the Set Default button. From that point forward, you can open .ics files and you’ll get an appointment form in Outlook with buttons to Accept, Tentative or Decline.