MBX Mailbox file format
 
by Michael Santovec (michael_santovec@prodigy.net)
 
 
 
 
 
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Notes on file formats:
 
- Character strings are represented by the following notation: "ABCXYZ"
 
- Hexadecimal strings are resented by the following notation: x'012DEF'
 
- Binary numbers are stored in the normal PC format of least significant
 
byte to most significant byte. For example, decimal 266 (hex 10A) would be
 
stored in a 4 byte field as x'0A010000'
 
- Field locations are given in both absolute decimal (relative to 1) and
 
hexadecimal offset (relative to 0). For example: "1-16 (0-F)" indicates a
 
16 byte field that starts at the beginning of a record.MBX File Format
 
 
 
 
 
This file consists of a file header followed by 0 or more messages.
 
 
 
MBX File Header Length 84 bytes (hex 54 )
 
- 1-4 (0-3) - 4 byte character string "JMF6" - file id
 
 
 
- 5-8 (4-7) - 4 byte hex string x'03000101' - ?
 
 
 
- 9-12 (8-B) - 4 byte binary number - number of messages in the file,
 
including messages marked for deletion. This number only goes down when
 
the file is compacted.
 
 
 
- 13-16 (C-F) - 4 byte binary number - last used message number. Each
 
time a message is added to this file, this number is incremented and used
 
as the message number. This number never goes down, even when the file is
 
compacted.
 
 
 
- 17-20 (10-13) - 4 byte binary number - size of this file in
 
bytes.
 
 
 
- 21 (14) - 1 byte hex string x'01' - ?
 
 
 
- 22-84 (15-53) - 63 byte hex string, all x'00' - ?MBX Message
 
 
 
 
 
Each message consists of a message header, the message text, and an
 
optional padding field.
 
- 1-4 (0-3) - 4 byte hex string x'007F007F' - start of message id
 
 
 
- 5-8 (4-7) - 4 byte binary number - message number
 
 
 
- 9-12 (8-B) - 4 byte binary number - total size of the message including
 
the message header, message text and any optional padding field
 
 
 
- 13-16 (C-F) - 4 byte binary number - size of the following message text
 
 
 
- 17-? (10-?) - character field, size specified in previous field - the
 
message text exactly as received from the POP3 server. This includes the
 
e-mail headers (e.g. From:, To:, etc.), and any encoded attachments.
 
 
 
- ?-? (?-?) - 0 to 3 bytes hex string, all x'00' - the size of this field
 
varies to make the whole message a multiple of 4 bytes long. However, as
 
long as this field is properly accounted for in the above total size of the
 
message, this field can be any length and the mail program will
 
workproperly.
 
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