[Tracker] indexing regular mbox files

[Ben Gladwell <bgladwell goantiques com>]

I searched the archives for this, but sorry if this has already been
asked.

I don't use Evolution or Thunderbird.  I just have some mbox files
sitting in a directory in my home directory that I would like Tracker to
index.

tracker-preferences seems has an option under the Emails tab that says
"Mailboxes - Additional mbox mailboxes to index".  However, its grayed
out.  Also, .config/tracker/tracker.conf doesn't have a section for
this.

Is it possible to index mbox files?

Thanks,

-Ben