dovecot - Sep 2006 - TAB characters in subject header continuation/wrap lines

I have some emails where the Subject line has been wrapped, and
subsequent lines are indented with TAB characters. Specifically, here's
a dump of a portion of an email:

0002020   C   c   :  sp  nl   S   u   b   j   e   c   t   :  sp   [   B
0002040   u   i   l   d   b   o   t   ]  sp   B   u   i   l   d   B   o
0002060   t  sp   S   U   C   C   E   S   S  nl  ht   (   B   l   d   _
0002100   g   s   s   d   k   _   g   s   s   d   k   _   t   e   s   t
0002120   _   2   0   0   6   _   0   9   _   1   2   _   0   0   _   0
0002140   1   _   0   0   _   I   n   c   r   e   m   e   n   t   a   l
0002160   _   2   )  nl   X   -   B   e   e   n   T   h   e   r   e   :

Note the HT about half way through the third line.

When I view this email using Thunderbird 1.5.0.5 on Windows XP, with
Dovecot 1.0.rc7 running on CentOS 4.3, this TAB character shows up as a
funny character in the subject line, as displayed by the Thunderbird.

My question is: Should Dovecot be detecting mail header continuation
lines that start with a TAB, and stripping the TAB (converting to a
space)? I *think* that's what the RFCs implied when I read up on this a
few months ago, but I may easily be mis-remembering.

A second somewhat off-topic question: When the automated system that
sends out these messages sends them to me directly, this problem does
not occur, because the email titles are not wrapped. However, when I
receive these emails via a mailman mailing list, mailman prepends the
text "[Buildbot]" on the front of the title, thus making the title
long
enough to require wrapping. As such, I imagine that it's mailman that is
indenting the Subject continuation line with the TAB character. Is there
an issue in mailman - should mailman be indenting with e.g. a SPACE
character, or is mailman's action perfectly legal?

Thanks for any pointers.

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Stephen Warren wrote:
> My question is: Should Dovecot be detecting mail header continuation
> lines that start with a TAB, and stripping the TAB (converting to a
> space)? 
No.  Dovecot should not alter the message at all.  There is an older bug 
in bugzilla about this; it is the MUA that is at fault here.  The 
leading tab is FWS (Folding White Space) and can be added by clients 
(Exchange is particularly prone to do this) and should be ignored by 
everything up to and including the local MUA.
> Is there an issue in mailman - should mailman be indenting with e.g. a
SPACE
> character, or is mailman's action perfectly legal?
Not just legal, but if the subject line would exceed 998 characters 
(plus CRLF) it is required that the individual lines be wrapped.

HTH

John


-- 
John Peacock
Director of Information Research and Technology
Rowman & Littlefield Publishing Group
4501 Forbes Boulevard
Suite H
Lanham, MD  20706
301-459-3366 x.5010
fax 301-429-5748