.MSF File Extension

Mozilla Thunderbird Mail Summary File

Miscellaneous File
The .msf extension (Mail Summary File) is used by Mozilla's Thunderbird email client. Thunderbird stores the user's mail in two files, one without an extension (E.g Inbox) which holds the actual mail messages in the standard 'mbox' format and the other with an .msf extension (E.g Inbox.msf) which holds an index of the mail.

These files can be found in the following locations:

Windows Vista
C:users[User Name]AppDataRoamingThunderbirdProfiles

Windows XP/2000
C:Documents and Settings[User Name]Application DataThunderbirdProfiles

Windows 95/98/ME
C:WINDOWSApplication DataMozillaThunderbirdProfilesxxxxxxxx.default

To convert Thunderbird emails (mbox format) to eml files (used by Microsoft Outlook and Microsoft's Outlook Express), you will need a tool such as IMAPSize.

Other .MSF file extensions

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    Comments (7)
    showing 1-7
    tonybaker33 _at_ hotmail.
    2007-05-05 09:58:13
    Thanks for the information. Can I use these files on my mac?
    2007-07-10 15:05:02
    I like ordering my messages by thread. Occasionally I'd like to add a message to a thread or merge two threads. I thought the easiest way would be tweaking the .msf file, but I can't find any useful info and reverse engineering the format seems too time-consuming an effort. Any suggestions? Thanks.
    2008-07-21 12:00:41

    Yes. In fact, what the above information does not include is any mention of the fact that Thunderbird Mac also creates .msf files as well as the no-extension "box" files
    (i.e.: "JunkMail", no quotes).

    I just brought one of my .msf files over from the boot drive of a G4 (Dual 1.25Ghz 80/40/1GB RAM, OS X 10.3.x) on which I was using T'bird almost exclusively [occasionally Mozilla Mail, but not often]. So there's your proof. As for using a Windows-created .msf in Mac OS X's build of T'bird, I'd say it's worth a shot.

    Refugee from the 'Elegant OS'
    2009-06-21 14:37:05
    I had thunderbird once and hated it and now all of my documents I saved have the msf on them and will not open. I do know thunderbird changes the settings. How do I get them back to outlook express so I can open them.
    2009-08-29 05:52:43
    I am a nut about saving all email including the attachments. I am currently using Windows Mail Client that came with the Vista operating system. I will soon replace Vista with Windows-7 which I am told does not contain the Windows Mail client.

    I am tired of changing mail clients every time Bill Gates has thinks he has a better idea and would like to stick to one that will be around for awhile.

    Before switching to Thunderbird, would you please answer the following questions? Do email attachments save embedded in the emails to my computer? Can saved emails be read with a program other than Thunderbird? Can copies of emails be saved in a folder of my choice.

    Thank you for your time.

    michael thomas
    2009-11-26 06:03:50
    I cant open the messages that I have sent, in my Thunderbird sent box!
    Jim D.
    2009-12-26 16:29:46
    When I go to 'run' and enter the words 'profile manager (to create a new profile), I get a message that ThunderBird is running and needs to be shut down, even though I have completely shut it down. I get this message, even after un-installing ThunderBird.

    Because of this, I can not open my backup ThunderBird mail files.