[New-bugs-announce] [issue30428] mailbox.MMDF wrongly adds From_ header to file

[Ralph Corderoy]

New submission from Ralph Corderoy:

Class mailbox.MMDF supports the MMDF-mail-spool file format.  This is a file with zero or more records, each starts and ends with a line of four ASCII SOHs.  Within those two lines is an email in RFC 5532 format, i.e. a headers section followed by an optional body.  There is no "From_" header before the headers section as used by mbox format.

https://docs.python.org/3/library/mailbox.html#mmdf references http://www.tin.org/bin/man.cgi?section=5&topic=mmdf that explains this clearly and gives an example spool file;  there is no "From_" header.

mailbox.MMDF documents it produces a From_ header and does so.  This is wrong.  It's wrong in Python 2 too.

    >>> import mailbox as mb
    >>> f = mb.MMDF('mail.spool')
    >>> f.add('Subject: Python Bug.\nFrom: bug at hunter.com\n\nEnds.\n')
    0
    >>> f.close()
    >>> print(repr(open('mail.spool').read()))
    '\x01\x01\x01\x01\nFrom MAILER-DAEMON Mon May 22 10:14:02 2017\nSubject: Python Bug.\nFrom: bug at hunter.com\n\nEnds.\n\n\x01\x01\x01\x01\n'
    >>>

Other MMDF-handling software other than tin(1), e.g. http://www.nongnu.org/nmh/, neither produces a From_ header for MMDF, nor handles one being present.

----------
components: Library (Lib)
messages: 294138
nosy: ralph.corderoy
priority: normal
severity: normal
status: open
title: mailbox.MMDF wrongly adds From_ header to file
type: behavior
versions: Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue30428>
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