Comment 53 for bug 849416

This issue has really annoyed me for a while now. I used to use mutt to handle the multipart/alternative calendar attachment until I came across this thunderbird addon:

https://addons.mozilla.org/en-US/thunderbird/addon/show-all-body-parts

It does the trick but requires an extra mouse/menu/click when viewing a meeting invite email.

FWIW, I really like how Claws Mail handles these multipart/alternative parts. It has a couple action icons on the right of the message window (one icon per multipart and others for real attachments).