For the last few weeks when I am typing an email the screen will freeze, then a rotating circle will appear and then I can type again. It has been increasing in frequency. Today it is freezing on every line, I have to wait 30-40 seconds, then I can type again for another line, etc.

Also when I am reading my downloaded emails it will freeze and I will get a message at the top left next to the word Thunderbird that says "Thunderbird (Not responding)".