[New-bugs-announce] [issue12649] email.Header corupts international email header and ignores maxlinelen in some cases

[dandre]

New submission from dandre <andre.d at gmx.net>:

Hello there, first of all, thank you all for Python. I didn't know it was so great; otherwise I'd have checked it out before.

Using 2.7.2 MSC v.1500 32 Intel bit for now.

Playing with email.header, I came across an odd behaviour.

Attached please find a script which demonstrates that
1) maxlinelen is ignored and
2) header fields are split in a manner not suitable for all systems involved in email processing.

The script will print the headers. They're all the same and extend over two lines; both should probably not be the case, although it dosn't hurt in itself.

If you uncomment the SMTP part of the script and send that email to yourself, you'll probably see that the From: and To: header will be misinterpreted by your email client; I tested this with two different email providers. Looking at the raw data which are received, it appears that at least in one case, a system along the way added a comma between the two "To:" lines. This is something which one should easily be able to avoid, if only the maxlinelen would be obeyed...

Having taken a look at email.header.py, it appears to me that the semantics of _encode_chunks() does not exactly match its documentation due to the results of (at least some) charset.header_encode() calls. What seems to happen is that charset.header_encode() can return several lines already, and it will apparently split the line without any deeper knowledge. As a result, the Header module will not apply its sophisticated maxlinelen/splitchars logic. The header is split at some pretty arbitrary point and not all systems appear to be happy with that, although the relevant RFC apparently only reads "SHOULD" in this regard.

----------
components: Library (Lib)
files: email_header_bug.py
messages: 141290
nosy: dandre
priority: normal
severity: normal
status: open
title: email.Header corupts international email header and ignores maxlinelen in some cases
type: behavior
versions: Python 2.7
Added file: http://bugs.python.org/file22783/email_header_bug.py

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<http://bugs.python.org/issue12649>
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