please see how to transfer data or regain data, more info here(option-3). and also please wait for other supporters to help you further here. keep auto-update disabled.

atErik Thanks but I tried to create a new profile and copy but the data in the default profile seems to have been damaged. I had to reestablish all email accounts. That seems operational except all the email that was deleted is back in the inbox. Most damaging is all the email I had seperated out into local directories is gone. Where was the local directories stored?

local directories are inside the "profile" folder.

profile-name looks like: "xxxxxxxx.default-bak" , "xxxxxxxx.default" , "xxxxxxxx.default-release", etc

TB's "profile" folders are kept inside here "%APPDATA%\Thunderbird\Profiles\" which usually equals to "C:\Users\<WindowsUserName>\AppData\Roaming\Thunderbird\Profiles\"

Local Folders & all sub-folder & emails are here: "...\Profiles\<profile-name>\Mail\Local Folders\"

those links i mentioned, that has info on this.

At least in my case there was no "xxxxxxxx.default-bak". And as I mentioned the default profile was corrorpted or something and did not have any data for my established email accounts. Luckly I had stored a backup of "AppData" that although old was able to copy in to a new defualt profile I created and get back to operational except the address book is still messed up. In older versions the contacts were in abook.mab. This no longer seems to be the case. How can I get the contacts from an old abook.map into the new file?

there are multiple .mab files, that are responsible to contain your address book. only TB v68 series & versions before that, can use .mab files.

TB v78 series & newer versions uses .sqlite based address-book files, and cannot use .mab address-book. ( new TB can convert mab into sqlite on when run in a v68 based profile 1st time )

findout what exact profile folder name is used by your new v78 series TB: TB main menu > Help > Troubleshooting information > about:profiles > Root folder > write down the last folder. lets call it "new-TB-profile". thats what you will see inside this folder: "%APPDATA%\Thunderbird\Profiles\"

it was avery good thing that you had backup of all app's all settings in C:\Users\<WindowsUserName>\AppData\ folder.

so, if your old backup has mab files, then, you will need a TB v68.12.1 to get back your older address-book. you can use a second-TB (shown in option-2) here.

but, if your old backup has NO *.mab files (and also no *.mab.bak files), & instead have just *.sqlite files, then copying these 3 files : abook.sqlite , history.sqlite , impab.sqlite inside the v78 new profile "new-TB-profile" will bring your older address-book back . there will be other sqlite inside new-TB-profile, do not overwrite those.

more-info on Address-Book.

if you have added some new contacts inside the new v78 series TB's address-book , then make a backup of all sqlite files again which are inside new-TB-profile , before overwriting with above mentioned older 3 files.

if you did not import address-book earlier in your old TB , then you will not have impab.mab or impab.sqlite files, etc.

while TB is running, then do not do file-operations. exit out of TB, & do file-operations , then start TB again.

once second-TB is running , then you can copy Contacts from v68 series TB, manually, into new v78 series TB.

EDIT: added link for address-book more-info.

atErik In another bit of luck I had mothballed my previous main computer after putting a new build online before it got the present Thunderbird update. So was able to export addresses as .csv files then import into the present computer with the corrupted address book. Might have lost 1 or 2 recent additions

Thinking of putting the mothballed computer to use for a project. Will the latest Thunderbird update still corrupt address and the mail accounts?

If you have any suggestions or questions please let me know. Thanks

latest TB v78 series, uses different format of address-book , sqlite format. v68 uses mab format address-book. two different things. when a address-book is very simple , that is, it does not have any custom or unknown or complicated columns/items, etc , then v78 series can convert v68's mab files, into sqlite , otherwise it fails to convert. (i guess, when TB devs will improve it or if they improve it , then it will be less-problematic)

make a backup of all TB-profiles in that other computer too. so if you can access older address-book (v68 series TB) , & make it simple. there is no restriction on how many contacts you will add. so if needed make multiple entry , but not complicated columns or other complex characters.

then if you decide to update/upgrade into v78 series TB , v78 series will/should be ale to handle it.

if you put all mab files in an old TB profile , & run v78 series from commandline to use that profile , then v78 can also convert mab into sqlite , if the mab Contacts are not complicated,etc.