Try this: launch in safe/troubleshoot mode (hold Shift when starting TB), check 'reset toolbars & controls', 'make changes & restart'.

If that doesn't help, create a new profile and add your (IMAP) accounts: Windowskey+R, type

thunderbird.exe -p

and create a new profile. Address books, local mail, filter rules etc. can be transferred from the old profile to the new if necessary.

Many thanks for your help. The shift-start didn’t work, but the new profile enabled me to get going with my main email addy so this leads me to my next questions…

1. I use QuickFolders. Is there a simple way to copy the settings?

2. Where are the filter rules located - what do I copy?

3. As 2 for everything else I need.

4. Do I have to add all other email addresses one by one, or can I copy those too?

Thanks, Tony

Oh… where is this new profile now? I closed TB but when I open it from the desktop icon I’m back to the original broken one.

Forget that last question - I’ve managed to find the new profile to use as default.

Many thanks for your help. The shift-start didn’t work, but the new profile enabled me to get going with my main email addy so this leads me to my next questions… 1. I use QuickFolders. Is there a simple way to copy the settings? 2. Where are the filter rules located - what do I copy? 3. As 2 for everything else I need. 4. Do I have to add all other email addresses one by one, or can I copy those too? Thanks, Tony

1. The settings can be exported and imported, but if the previous profile can't be opened, there is probably a way to copy the settings manually. If the old profile can't be opened in safe mode, delete xulstore.json from the old profile (same as 'reset toolbars...'), then see if it can be opened in normal mode.

2. msgFilterRules.dat in the account subfolders of Mail and ImapMail in the profile can be copied between profiles and accounts.

3. abook.sqlite and history.sqlite (Personal Address Book and Collected Addresses) can be copied from the old profile to the new. Other sqlite, mab, LDIF etc. address books can be imported from Tools/Import.

4. Add the IMAP accounts again and mail on the server will download on first sync. Mail in POP or Local Folders can also be copied manually.

If the old profile can't be opened in safe mode, delete xulstore.json from the old profile (same as 'reset toolbars...'), then see if it can be opened in normal mode.

Thanks for the suggestion but that doesn’t work either. I’ve spent ages comparing the contents of the two profile folders to see if anything jumps out at me (like a wildly different file size) but there’s nothing obvious that I can see.

I’m sure that replacing a single file somewhere will fix the old profile but I’m darned if I can see what it might be. Probably because I don’t know what most of the files are for!

Regards, Tony