About Thunderbird Mail
- Julie Wetherill
Thunderbird (TB) stores each mailbox in a separate MBOX file (with no file extension). Attachments are stored with the associated email message inside the MBOX file.Â
Where does Thunderbird store email files?
Thunderbird stores all mail content, address books and settings in a directory called "profile".  The profile is stored outside of the program directory to avoid data loss during upgrades. More than one profile may be defined and each profile can be associated with more than one email account.
Note: On Windows 2000/XP/Vista, the folder containing your user profile data is hidden by default and you will need to show hidden files and folders to navigate to the profile folder.
Windows
Default path to the TB profile on Windows 2000/XP:
  C:\Documents and Settings\<user name>\Application Data\Thunderbird\Profiles\<Profile name>
Default path to the TB profile on Vista and Windows 7:
  C:\Users\<user name>\AppData\Roaming\Thunderbird\Profiles\<Profile name>\
Mac OS X
Profile directories are in one of these locations:
.../Library/Thunderbird/Profiles/<Profile name>/
.../Library/Application Support/Thunderbird/Profiles/<Profile name>/
Additional strategies for locating the profile are described in the MozillaZine knowledgebase article about Thunderbird profiles: http://kb.mozillazine.org/Profile_folder_-_Thunderbird .
How does Thunderbird store email files?
Mailboxes are represented by a pair of files: an MBOX file with no extension and a companion indexing file with the same name and .msf extension.Â
Within the Thunderbird profile, mailboxes are stored in a subdirectory named after the mail server. In the following example, the INBOX is nested inside a directory named after the associated mail server (hulmail.harvard.edu):
...\Thunderbird\Profiles\s3wyz8of.default \ImapMail\hulmail.harvard.edu\
              INBOX
              INBOX.msf
Thunderbird allows you to create a hierarchy of mailboxes. On the file system, this hierarchy is represented by a subdirectory named after the parent mailbox (with a .sbd extension), and a mailbox file nested inside. For example, if the user creates the mailbox IMPORTANT and nests it below the INBOX, the file system would look like this:
...\Thunderbird\Profiles\s3wyz8of.default \ImapMail\hulmail.harvard.edu\
              INBOX
              INBOX.msf
              >INBOX.sbd
                             IMPORTANT
                             IMPORTANT.msf
Some levels in a mailbox hierarchy might involve just a directory and no mailbox. In this case, Thunderbird will still create a mailbox file in addition to the.sbd directory, but the mailbox file itself will be empty. In the following example, the user has nested the mailbox "Planning" inside a directory and subdirectory:
...\Thunderbird\Profiles\s3wyz8of.default \ImapMail\hulmail.harvard.edu\
              INBOX
              INBOX.msf
              EAS-project (empty mailbox)
              EAS-project.msf
              >EAS-project.sbd (directory)
                             Phase1 (empty mailbox)
                             Phase1.msf
                             >Phase1.sbd (directory)
                                            Planning
                                            Planning.msf