Emails in Thunderbird are stored as a piece of text in an mbox file, when you choose to save as .eml file they become a new file. As you may know, all files and folders on any computer that are newly created will have the date of when they are created. But this is a bit of a pain when you would like to easily locate emails stored as .eml files and use the 'date' the email was sent. What you need is to get the date of email added to the name of the .eml file. You could do this manually by renaming the file when you create the file, however that is a bit laborious. Use this addon extension: ImportExportTools * https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/ How to install addon extension info: * https://support.mozilla.org/en-US/kb/installing-addon-thunderbird After installing and restarting Thunderbird at prompt.... In the 'Addons Manager' tab, you will see the name of the addon extension. * click on the ImportExportTools 'Options' button * click on 'Filenames' tab Customise the format for Filenames. * select 'use following format' * select 'Subject' 'Name/Sender' and 'Date.......But you can set whatever you prefer. * click on OK Now your preferences are set up.... Right click on highlighted email(s) and select: * 'Save selected messages' > 'EML format' * choose where to save them.