An attempt to solve the problems in the Unix mbox format with respect to lines starting with the string 'From '.

A header named 'Content-length:' is introduced into the headers at the beginning of every email, which specifies the length of the body of the email. That way programs can tell where individual messages end without looking at the 'From ' lines.

This scheme, while seemingly elegant, has a few serious problems:

  • handling of the emails by unaware software (or users using an editor) makes the Content-length header wrong and breaks the whole system (thus the scheme is fragile)
  • there is no precise specification of the semantics of this header (e.g as how many characters line endings are counted)
  • programs can't tell whether a given mail file uses this scheme or not, since the 'From ' lines will still be there

All in all, this format, introduced by Sun, should not be used.

There is a detailed discussion of the problem in this thread:

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