there are tools to backup and restore emails. but i prefer to do it the old fashion way - by directly copying the files.

where are the files

to find physical location of where emails are stored, from menu > tools > accounts settings, go to Server Settings and look for Local directory at bottom of screen. this is where the files are. this directory will be referred to as the mail directory.

to go to the mail directory , copy string from Local Directory field. go to windows start button > run..., paste the copied string into the field, which brings up windows explorer and goes directly to this directory.

backup and restore

backup emails by copying files from the mail directory.

if for any reason your email files are corrupted, you can just copy all these files from backup back to the mail directory.

to backup specific set of emails, it's best to create a folder in thunderbird and move those emails to this folder. all mails in a folder is stored as single file in the mail directory.

you will find 2 files corresponding to each folder, in the format of <folder name> and <folder name>.msf.

to restore specific set of emails, locate the set of files correspond to the folder name and copy back to the mail directory.