I get the "Not Responding" error and unacceptably slow performance with Thunderbird 68,6.0 on my Dell T3600 workstation with 16 Gb ram and a fast processor. I have no such trouble on my Thinkpad laptops with 8/256 and 16/512 specs. Windows is up to date as is Thunderbird. I have followed many recommendations (exclude the antivirus exe in Windows defender, delete all .msf files and reset thunderbird, and so on). Some of these things seem to help briefly, and then Thunderbird reverts to Not Responding. It just did that now in the background when I was not using or touching Thunderbird at all. I hope there is some help for this. Thanks.