I use windows backup to backup the contents of my thunderbird profile in situ. However if you do not use a backup program do it manually. Just make sure Thunderbird is no running when you do it.

The storage location to be backed up is dependent on your user account on the OC and the windows version. So press the windows key +R and type %appdata% into the dialog and press enter. THat will drop you into the correct folder every time. In the windows file manager that opens, copy the Thunderbird folder and any sub folders to your backup device. This will be a significantly larger backup that your windows mail ever was.

Matt Thank you. I followed your guidance and can now see a list of the folders in the back up hard drive. Each folder is labelled type File or MSF File. From the size I am assuming that the messages are stored in the File. Two questions if thats OK: 1. if I had to migrate them back to a computer would you expect them to successfully load? 2. A double click on a folder opens the image "how do you want to open this file?" Which app should I use?

Thank you

The true mail is stored in mail and imapmail folders and sub folders in very large files accompanied by an MSF file. However you should be backing up everything in the profile, not just the mail, that way if something happens it is just a matter of copying things back to their oringinal location to replace a corrupt installation, or move to a new device.

Many thanks Matt. Very grateful to you.