This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Natao arisiva ity resaka mitohy ity. Mametraha fanontaniana azafady raha mila fanampiana.

Can't Delete Events from Lightning Calendar Connected to Outlook.com via iCalendar (ICS)

  • 2 valiny
  • 1 manana an'ity olana ity
  • 1 view
  • Valiny farany nomen'i john76

more options

I've successfully connected Lightning to an Outlook.com calendar using the iCalender (ICS) protocol. However, when I try to delete an event from Thunderbird/Lightning, I get this message:

Error Code: MODIFICATION_FAILED Description: If you're seeing this message after snoozing or dismissing a reminder and this is for a calendar you do not want to add or edit events for, you can mark this calendar as read-only to avoid such experience in future. To do so, get to the calendar properties by right-clicking on this calendar in the list in the calendar or task view.

And under Edit > Calendar Properties, "Read Only" becomes re-checked. If I uncheck it again and attempt to delete an event, I get the above message again (and the event does not delete).

So how can I successfully delete events in Lightning?

I've successfully connected Lightning to an Outlook.com calendar using the iCalender (ICS) protocol. However, when I try to delete an event from Thunderbird/Lightning, I get this message: Error Code: MODIFICATION_FAILED Description: If you're seeing this message after snoozing or dismissing a reminder and this is for a calendar you do not want to add or edit events for, you can mark this calendar as read-only to avoid such experience in future. To do so, get to the calendar properties by right-clicking on this calendar in the list in the calendar or task view. And under Edit > Calendar Properties, "Read Only" becomes re-checked. If I uncheck it again and attempt to delete an event, I get the above message again (and the event does not delete). So how can I successfully delete events in Lightning?
Sarin'efijery napaingotra

Novain'i john76 t@

Vahaolana nofidina

Updating this in case anyone runs across it. You'll want to use the TBSync add on. It works really well.

Hamaky an'ity valiny ity @ sehatra 👍 0

All Replies (2)

more options

Well, here's the answer: https://thunderbirdtweaks.blogspot.com/2016/10/outlook-calendar-in-thunderbird.html

At the bottom of that article, in the comment section, someone posted this link for the latest add on file (2019) that you'll want to use: https://github.com/ExchangeCalendar/exchangecalendar/releases

more options

Vahaolana Nofidina

Updating this in case anyone runs across it. You'll want to use the TBSync add on. It works really well.