I'm sure this question has been asked a million times before, but my google and SE search-fu is failing me today.

One of my e-mail host recently shut down. I was naive enough to trust Thunderbird's settings of keeping offline copies and "never deleting" to not allow messages to be removed from my local copy. However, rather than deny login access to the mail server, it looks like the old host wiped my mailbox.

I have an INBOX and INBOX.msf that are not anywhere close to 0K in size (and an INBOX.sbd directory that is), so I'm hoping that the content is in the INBOX+msf, waiting to be undeleted and extracted/exported. So, other than opening this file in Thunderbird, what are my options to read or universally archive my Inbox files (that doesn't have the risk of me accidentally logging back into the server and re-creating the problem)?

  • Those settings, I believe, aren't applicable to IMAP. They are for POP3. With IMAP everything is done in the server. – GabrielaGarcia Oct 26 '18 at 19:22

The INBOX file is a standard mbox-format file (mboxcl2 to be specific) containing email messages in plain text form (the same as they were delivered in). Open it in a text editor and see what's inside.

To view a mbox via Thunderbird itself without it having any link to the original IMAP configuration, copy the file to <profiledir>\Mail\Local Folders\ (giving it a new filename of course). It can also be opened by other mail apps such as Mutt or Claws, and the messages can be uploaded back to an IMAP server.

INBOX.msf is a Mork database containing a "summary" of messages for faster access (essentially a lookup index for the otherwise-linear mbox file). It is useless.

INBOX.sbd contains "subfolders" – other mail folders that live under INBOX/. They all have their own mbox files (and .msf indexes).


I have found that copying the file to \Mail\Local Folders\ does not always work. Great when it does, but sometimes the Mailbox does not show up.

The TBird files are text. Many text editors have a "Search In Files" function that will return a list of linked snippets. I use Visual Studio Code.

The latest version of FileLocator Pro has this capability: https://www.mythicsoft.com/filelocatorpro/information/#version-history I haven't tested this function, but I've used the Lite version to search Word Docs and it works great. They have a trial version of the Pro.

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