title: A cancel .ICS works in Outlook Windows App but not Outlook 365. Why?
body: <p>I'm a novice programmer trying to send colleagues staffing assignments, from an outdated DB, as .ICS files. I've gotten the following things to work swimmingly in Outlook Windows:</p>
  <ol>
  <li>Add a single event with an .ICS attachment</li>
  <li>Add multiple events with an .ICS attachment</li>
  <li>Cancel a single event with an .ICS attachment</li>
  </ol>
  <p>So what's the problem? Many of my colleagues use Macs, and I can't get the cancel-event to work with Outlook for Mac OR Outlook 365. On the latter, I'm getting the dreaded &quot;Couldn't import calendar. Try again later.&quot;</p>
  <p>I'll paste in a sample below, but I'm confident I have the formatting right (and have checked it with a validator); UID is constant; Sequence is incrementing; Last-Modified is updating. I've tried both &quot;Method: Request&quot; and &quot;Method: Cancel&quot; with no change.</p>
  <p>I've also read through countless posts and understand this is a long-standing issue.</p>
  <p>Right now my best guess is that this isn't an issue with the ICS itself, but with the MIME Content-Type in the Email header. I've confirmed that this is NOT being set as text/calendar, but I don't know of any way to change this.</p>
  <p>Hope that's enough info. If anyone has any insight on how I can make this work, would be grateful.</p>
  <pre><code>BEGIN:VCALENDAR
  VERSION:2.0
  PRODID://Workplace//EN
  METHOD:REQUEST
  BEGIN:VEVENT
  UID:F499BCFD-16DB-2A40-B1E1-F8D64F6A9B36
  SEQUENCE:5
  DTSTAMP:20210630T165316Z
  ORGANIZER;CN=Live Programs:
   MAILTO:XXX@xxx.org
  ATTENDEE;ROLE=REQ-PARTICIPANT;
   PARTSTAT=TENTATIVE;CN=Matt P
   :MAILTO:ZZZ@zzz.org
  DTSTART:20220703T154500Z
  DTEND:20220703T164500Z
  LAST-MODIFIED:20210713T134505Z
  LOCATION:Theater One
  SUMMARY:12:00pm Show (Presenter)
  STATUS:CANCELLED
  END:VEVENT
  END:VCALENDAR
  </code></pre>