My problem is that about 2 weeks ago, Thunderbird inexplicably partially seized up. It will now only open ONE 'Folder' at a time - for example, Inbox, and will allow me to scroll through that folder, and read any of the text (words) in the body of the email. (I can also Reply to/ or Forward / any of those emails.) HOWEVER, what I can NOT do, now, is then click on the "Sent Mail" box - and see any of the emails there. (The emails that continue to show still belong to the Inbox). Even though I have now clicked on the Folder 'Sent Mail' to open it. The only way that I can see the list - and read - the emails in my Sent Mail box, is to Quit Thunderbird, reopen it, (having carefully left the pointer on the choosen Sent Mail, before Quitting!), and then once it has reopened Thunderbird again, I can now click on Sent Mail. Then I can see and open all all of that mail, in Sent Mail - BUT ... I cannot go back to say 'Inbox', or any other Folder! It is now frozen on that one Folder, 'Sent Mail', and will not move to any other Folder - unless I *first place the pointer on the next Folder I want to look at, Then *Quit Thunderbird, then *open up Thunderbird again, and then I can look at the contents of the next chosen Folder!! Incredibly infuriating and tedious! WHY has Thunderbird frozen up like this? And what can I do to rectify this problem, pleeeease!? Help! I have an iMac, and a MacBook Air. Thunderbird keeps seizing up on both of them. I have version - 52.6.0 (64-bit). It says I am "currently on the release update channel) - whatever that means!