For some while I've had a Windows 10 desktop and a Windows 10 laptop. I used to keep my mail using Thunderbird in sync on these two machines by just copying the profiles from one to the other. Just recently the laptop stopped working so I got another, which came with Windows 11. I duly installed Thunderbird on that and copied the profiles from my desktop to it, and it happily worked. However when I copied the profiles back from the laptop to the desktop Thunderbird said something like "you've started an old version of Thunderbird with new profiles - you'll have to set it all up again." Is that true? Is there a version of Thunderbird for Windows 10 which will acccept the profiles from the Windows 11 version? Is there some routine that will convert the Windows 11 format profiles etc to the format used by the Windows 10 version? When I look at Apps & features in Settings on Windows 10 it says that Thunderbird is "Mozilla Thunderbird (x86 en-GB) 115.13.0" Help About on Thunderbird on Windows 11 says it is 128.0.1csr (64-bit) Thank you Regards Alan Sandell