Thunderbird Message File
From Just Solve the File Format Problem
Thunderbird is able to save the messages in the .eml files. These are basically almost the exact text that Thunderbird has received from the mail server (the Internet e-mail message format). The headers (as is the case with the email protocols) are separated from the body of the message by an empty line. The body is saved in the form that is appropriate for that message (for example it can be saved as a multipart block).
