Calendar cancellation does not send email

...Even though I tell it to send one.

What do you mean by calendar cancellation? Calendars can be deleted but there is no message related to that process. If you are talking about cancelling an event, how did you "tell" the application to send an e-mail? If you are in the edit mode for a calendar event and you click cancel that does not cancel the event. Clicking the cancel link cancels the editing of the event and does not delete it (remove it from the calendar).

I clicked on an event in the calendar. I clicked on "delete event". I clicked the check mark "Notify subscribers via email about this change/cancellation". I then clicked on "only this event" as it was one event in a series. No email was sent.

In my testing only a repeating event has an option to send a message when deleting an event. Without disturbing a bunch of people while I conduct tests I did not select this option. There is nothing to indicate when the message will be sent. There are two possibilities based on when messages are sent when creating events. The first is now and the other is at some point before the event is to occur. If the latter, then the specified time would be tied to the message send time specified when the event series was created.

Just for the sake of investigation, was "Send an email about this event" selected when the event series was created? If so what was the specified time for the message to be sent?

Yet another case where a delete did not send an email. In addition, I made a change to 1 event in a series changing the time and notes. There was a check mark to indicate that a notification should be sent to subscribers. I clicked the check mark, and updated the single event. No email was sent.