The Windows mail client is used to send and receive e-mail locally on the Windows operating system. If you are switching mail clients from the built-in Windows client to the open-source Mozilla Thunderbird client, you can transfer your e-mails from Windows Mail to Thunderbird with the help of a plug-in for the Thunderbird mail client, recommended by Mozilla.
Download the ImportExportTools plug-in for Mozilla Thunderbird (see the Resources seection of this article). Save it to the main Thunderbird folder in your \"C:\Program Files\Thunderbird\" directory.
Open Thunderbird, click \"Tools,\" click \"Addons,\" click \"Install\" and browse to the file you saved in Step 1. Click \"Open,\" click \"Install\" and then restart Thunderbird.
Click on the \"Tools\" button, click \"ImportExportTools\" and then click on the \"Browse\" button.
Go to the \"C:\AppData\Local\Microsoft\Windows Mail\" directory and highlight all of the files that end with the .EML extension.
Click on the \"Import\" button and the e-mails from your Windows Mail program are imported into Thunderbird.