Comment 143 for bug 849416

The Calendly.com scheduling service is affected by this problem.

It's not helpful to decry that there exist implementations that are not spec-compliant. If the reality is that this issue is so widely deployed as to be defacto standard, then it needs to be treated as such. (That said, I'm not entirely convinced that it's a violation of the standard—the e-mail is essentially saying that text/calendar is the preferred format of the message, and text/html and text/plain are provided as the fallback. The bug in the sender, then, is that these other formats don't have all the details that the text/calendar message has.)

Thunderbird should be updated, if not to support the calendar item wholesale (since Thunderbird doesn't have a built-in calendar), at least know enough to convert it to an ICNS attachment that can be downloaded and used by an actual calendar app.