Upgrading Thunderbird on Mac 10.11.3 from 31.6.0 to 38.5.1 end up with "app not responding". Trying to "Get Messages" show the emails on the bottom line as "connected to Mail...." but nothing gets downloaded. To get out, need to do a "Force Quit". Tried to run Thunderbird as "Restart with Add-ons disabled" and it doesn't even start, show "App not responding" and need to "force quit" again. I have tried many previous upgrade of Thunderbird before (and on previous OSX versions) and with same result. Each time, end up having to restore to Thunderbird 31.6.0 with Time Machine and all is working back normally. Any suggestions or should I look for a different email client (cannot stay on older version indefinitely)? Thanks in advance for options.