I've been using Thunderbird for a good decade or more, and honestly it's got the best email filtering rules builder of any email client I've used. The spam detection has only gotten better at detecting junk spoofed emails over time, it also always displays the email address as well as the name so it's easy to spot when something funky might be happening and the recent UI tweaks they've been making are very well thought out. Oh and they added an option to export/backup your profile to a compressed archive so I no longer have to copy the same .thunderbird folder from computer to computer and every time I install a new Linux distro