I rely on the mail search box to find old email threads but even with the search settings set to "all" I only get the emails in the inbox at that moment, which I can already see for myself, so, not much help!
I am new to RC mail so it could be another settings issue I don't know about - any suggestions? Thank you!
You'll need to use a plugin like https://github.com/GMS-SA/roundcube-advanced-search to do a all folder search.
I think that you would be having some problems in your browser. My mail search is providing up every mail.