|Application Associated||Mozilla corporation|
|Category||email related data|
|Supported Platforms||Windows, Mac, and Linux|
MSF file extension belongs to mail summary file. It is a mailbox folder index that can directly open in a text editor but is not human readable. Each Thunderbird mail folder like Inbox, Sent, Drafts, etc is stored as two files: one without extension (for e.g. Sent), which is the Thunderbird mail file itself and the other with an .msf extension (for e.g. sent.msf), which is the Mail Summary File to the mail file. If the .msf file is damaged, Mozilla Thunderbird will display problems to accessing the affected Thunderbird mailbox folder. These files only contain an index of the message and mail headers and summaries.
These file can be stored in the following locations
Hexadecimal: 2F 2F 20 3C 21 2D 2D 20 3C 6D 64 62 3A 6D 6F 72 6B 3A.