Download and Launch Thunderbird Email Viewer Software. Press the Add File/ Folder button from the software's menu bar. Choose a file selection mode from options - Select MBOX file: - Select and Add Thunderbird Mail file manually. Select MBOX Folder: - Select folders containing TB mail files and add in bulk. Auto-Load Thunderbird profile: - Detect and add all Thunderbird Mail files in on click. Select and Add Thunderbird mail files/ folders from your local drive. Load all Thunderbird mail folders/ sub-folders and extract all mail items. Click on Thunderbird Email and preview email with complete info.