Recently I re-installed my system. I now use Thunderbird (78.2.1) and Windows 10. I backed up my old Thunderbird with Mozbackup. This created an archive file Thunderbird 68.11.0 (en-GB) - 2020-08-26.pcv The restore process failed to work. Mozbackup has not been updated for some time, and I was unwise to use it. When I reconnected Thunderbird with my web email supplier, the existing inbox and sent folders were repopulated from there. However my only ‘sent’ emails were those from my mobile phone, not my PC. Therefore I would like to restore my old ‘sent’ folder, saved by Mozbackup, but into a new local folder, perhaps called ‘Old Sent’. I can create a new local folder in Thunderbird. The problem is to populate it with my old emails. A Mozbackup .pcv file is actually another name for a .zip file. I can get at the individual folders backed up within the archive by copying it, renaming it as .zip, and I can then open it. I have two relevant files, now renamed as Old Sent , Old Sent.msf My problem is how to get Thunderbird to recognize the emails. Simply copying the two files into my current imap mail folder doesn’t work; Thunderbird ignores them. There is an ‘import’ facility in Thunderbird, but it isn’t obvious whether this would be able to do what I want. I see there are some add-ons that handle import to Thunderbird, but they don't appear to work with the latest version.