I'm curious, what issues did you encounter with Thunderbird?
I have found Thunderbird pretty wonderful overall. Using my Gmail as an example, I can select the "All Mail" folder (about 50,000 messages) and press Ctrl+Shift+K (for search) and it shows me results in just a few seconds.
I use Thunderbird to manage multiple email accounts, and it has been a huge time saver having it all unified in one place.