[Evolution] How to automatically forward invitations?

[Christophe-Marie Duquesne <chmd chmd fr>]

Hi evolution users,

I am trying to make a filter to automatically forward the invitations
I receive to another email of mine. I checked the source of the
invitations I receive and see that they contain the line
"Content-Type: text/calendar".

Unfortunately, most of these invitations are also multipart, meaning
that this line appears, but only in one of the parts, which means that
"text/calendar" is not one of the actual headers of the message. So
when I search for this header using the free form syntax
'header-contains:Content-Type=text/calendar', I do not get all the
messages I want to filter (close to zero matches).

I also noticed that the label $has_cal is set by some black magic on
those emails, but this apparently happens after the filter rules are
kicking in, and it generates errors in evolution when I try a filter
based on "label:$has_cal".

How can I achieve my goal? Any advice?

Best,
Christophe-Marie