This is resolved. After some googling, I inspected the file virtualFolders.dat in my pre-102, backed-up Thunderbird profile. Comparing this to the 102 copy of virtualFolders.dat, which was populated with only a few lines†, I noticed a difference in the form of the email account references: Old: mailbox://myusername@pop.mail.yahoo.co.uk New: mailbox://myusername%40yahoo.co.uk@pop.mail.yahoo.com †These few lines only existed because, after encountering this issue, I manually set the folders on a few of the Saved Searches. This turned out to be useful in terms of identifying the differences in the form of the account reference seemingly changed/required by Thunderbird 102. The fix was very simple, but obviously relies on having a pre-102 backup copy of your profile (or at least, virtualFolders.dat): # Make a backup of your current profile, in case things go awry. Example path to profile: C:\Users\<username>\AppData\Roaming\Thunderbird\Profiles\8tbwqop8.default # Locate the virtualFolders.dat file from the pre-102 backup (NOT the backup from step 1) # Make a copy of virtualFolders.dat file from step 2 and open the copy in an editor like Notepad++ # Find and replace the old account references with the new, as above # Save the file # Copy the file to your current profile e.g. C:\Users\<username>\AppData\Roaming\Thunderbird\Profiles\8tbwqop8.default # Open Thunderbird and check that Saved Search folders show messages i.e. that the issue is resolved