Hey Will, Many thanks for your help.
Apparently the content of my index_format varies from folder to folder. I also use %Z but I think, after having studied Mutt's documentation, that I do understand the problem. The manual says: %L If an address in the “To:” or “Cc:” header field matches an address defined by the users subscribe” command, this displays "To <list-name>", otherwise the same as %F. So my understanding is that it's because the list was Bcc'ed that it doesn't work. Worth noting is: as broken or inconsistent as it is, my currnet configuraiton does work for the too-many lists I am subscribed to. Thanks again, Seb.
