Meeting invitation contains “not supported calendar message.ics” file and other attachments

Today I received a Meeting Invitation that was received as a normal message but contained the following attachments;

  • not supported calendar message.ics
  • ATT00001.htm
  • c120414.ics

The ATT00001.htm attachment contained the same textual content as the meeting message, but trying to open either ics-file resulted in the error;

The operation failed.

How did this meeting invitation end up broken and how can I fix it so I can accept it and add it to my Calendar?

Not Supported Calendar Message.ics buttonThis Meeting Invitation was most like sent from an IBM Notes (formerly Lotus Notes) user and contains a recurrence pattern that isn’t compatible with the recurrence patterns available in Outlook.

Sometimes the ics-files can still be processed by another mail client and you can still get them into Outlook that way.

IBM Notes can also be configured to prevent sending out meeting invitations which can most likely not be processed by all Calendar applications.

Incompatible Recurrence Patterns of IBM Notes

IBM Notes buttonThe Recurrence Pattern engine for the Calendar in IBM Notes works very differently from the one in Outlook. Simply put, you could say that Outlook sends the recurrence calculation in the ics-file and that IBM Notes (often) saves the individual results in the ics-file.

This last method allows for a free-hand selection of dates as well as some exceptions and other options and patterns which will result in a broken invite for Outlook.

Some of these broken recurrence patterns and options are;

  • Exceptions for weekends
    • Move to Friday
    • Move to Monday
    • Move to Nearest Weekday
    • Delete
  • Recur monthly; Every xth and xth xday of the month
    • Example: Every first and third Monday of the month.
  • Recur monthly; xth day counting from the end of the month
    • Not broken but doesn’t count backwards so results in the wrong dates in Outlook.
  • Recur monthly; every xth and xth day of the month
    • Example: Every 3rd and 10th day of the month

Under some circumstances, Meeting Updates or Cancelation messages could also end up broken;

  • When sending an update/cancellation
    • This instance and all previous instances
    • This instance and all future instances
  • When there are exceptions to a supported recurrence and then add an Outlook user for all instances.

Opening your ics-file with Windows Calendar

Windows 10 Calendar App buttonInterestingly enough, the Windows 10 Calendar App can successfully process (most of) the ics-files generated by IBM Notes.

So when you are using an Exchange or account, you can configure that account in the Windows 10 Mail app and your Calendar will become available in the the Calendar app as well. When you then open the not supported calendar message.ics-file with the Calendar app, the meetings will be added and these will then sync to Outlook as well.

  1. Save the “not supported calendar message.ics” file to your Desktop.
  2. Right click on the file and choose; Open With-> Calendar
  3. When prompted “Which calendar would you like to add these events to?”, select your Exchange or Calendar.
  4. Press the button; Add to calendar

Within a few minutes, the Meeting will be added to your Calendar is Outlook as well.

These meetings will get imported as Appointments. Also note that the first occurrence of the meeting could get added to your Calendar twice.

Opening your ics-file with Google Calendar

Gmail buttonSimilar to the workaround with the Windows 10 Calendar app, you could also use Google Calendar to process these ics-files.

Simply forward the message to your Gmail address and open your Gmail mailbox in a web browser. You’ll now see an “Add to Google Calendar” link within the “Events in this message” box. Press the link and you’re done!

To get them into Outlook, you could do one of the following;

IBM Notes: Prevent sending out incompatible Meeting Invitations

NOTES.INI buttonIBM Notes users and Domino administrators can make changes at either client or server level or a combination thereof to improve the interoperability with Calendars of other email applications.

To values can be added to the NOTES.INI file for this;

You can click on the variables above to find out more details about how they actually work and their other possible values.

Domino administrators can also find more background information in the articles; Improving interoperability for users of calendars in e-mail applications other than Notes and Editing the NOTES.INI file.

Once these variables have been set, the Meeting page in IBM Notes will have a new “Some invitees use other mail programs” selection box which prevent you from selecting recurrence settings which may not work for other Calendar applications.

Enabling the “Some invitees use other mail programs” checkbox in IBM Notes will prevent users from creating incompatible recurrence patterns. (click on image to enlarge)
Enabling the “Some invitees use other mail programs” checkbox in IBM Notes will prevent users from creating incompatible recurrence patterns. (click on image to enlarge)