Hello, Until recently, I used Mail on my MacBook but when I retired I was advised to switch to Thunderbird. When I log into Thunderbird, things look OK (new messages download immediately but perhaps a little sluggishly) but if I try to write a message, as soon as I type the first or second letters of the "TO" line the little multicoloured wheel starts turning. At the same time, a few addresses that start with those letters come up, hang there for a bit and then the wheel disappears and the list of addresses is gone too!. If I then try to type another letter, the same thing happens all over again. I suspect this may have something to do with my address book? Looking forward to some suggestions.