[Mailman-Users] Block calendar invites to list

[francis picabia]

We have an issue where sometimes a person creates a calendar
item for an event, and canceling the item causes email to
be delivered to the list.

It seems the solution could be looking at MIME header tags
indicating it is a meeting invite, and we could block all
emails containing:

^Content-Type: text/calendar

Placing that in Spam Filter rule does not capture the email,
likely because it isn't in the top header section, but within
the MIME encoded sections.

Does this problem have a known solution?  Google didn't
find it and I don't see "text/calendar" in my archives of
the mailman mailing list.