Thanks for that Milo. I'll look further at the Bat, over this weekend if I get a chance. I've looked at their website already but have gleaned very little, especially about security issues. I don't need all sorts of fancy services, I just need to run about half a dozen e-mail accounts, find it secure and transparent and be able to migrate to it very easily and lose nothing in the process. I need a Thunderbird that works, really.....
My issues with Thunderbird seem not to be uncommon recently. As I have already related, I've spent ages trying to report my problems to anyone related to Mozilla who sets themselves up for that purpose but even that doesn't work for me and has driven me bonkers.
Thunderbird has worked so well for me for so long that my natural preference is to get it fixed and then stay with it. It's tricky, though, when I can't even communicate with them - nor them with me because they always want to do it by e-mail and that doesn't work, which is what I am about in the first instance!