Not knowing the layout of the bak file, you need to somehow extract the files as they would have appeared on computer. The thunderbird data would have most likely been in a folder named thunderbird that was appended to a folder named roamin, appended to a folder names appdata. If you can somehow create the extract of the bak and are unsure, just post a screenshot of the unzipped/exported BAK and we can assist

Thank you all.

I created a new (very small) backup file using MozBackup. I watched where the file went and it was the same format as the one I had from April 2025. I did a restore using the April 2025 one and everything came back. YEH!!!

So, if you have not done so, use MozBackup to backup your Thunderbird on regular basis and put it somewhere safe.

RIk

The mozbackup page has a warning about not being up to date yet, and there have been serious problems in the past from using that software. All I can say is to be careful. I have seen many users on this forum with mozbackups that failed to work.

David

I have received my new laptop. It is formatted win11 and I have extracted the files from my old backup.bak file. They are:

540s6w7f.default 540s6w7f.default.sbd aa8gnek7k3,default aahzhcejya.default-release bydluvx7.default-release m2rb14v0.default uqn7mizs.Default UserRik Mar 11 wjdncqx9.default 540s6w7f.default.msf

Does this information lead you to thinking of a way for me to get Thunderbird running on this new laptop with my old email files and contact? Any useful suggestion would be greatly appreciated.

Old guy Rik