How to Read/Open Thunderbird Mail File Directly? If you want to access Thunderbird mailbox files without installing the Thunderbird application, you can use eSoftTools Thunderbird Email Viewer Software. This tool allows users to open and read Thunderbird mail files directly from the system. It scans the Thunderbird profile data and displays all emails, folders, and attachments in a simple interface. Users can easily preview message content, check sender or receiver details, and access mailbox information safely without any data modification.