I would add that looking at how Roundup (a python based issue
tracker) deals with emails/mailing lists could provide some
interesting contrast to how they usually work.

http://roundup.sourceforge.net/
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I know there a branch for the mailing_list stuff. Just curious what the state is...and if you need to someone to work it.
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Also look at the Debian bug tracking system, if you plan to implement this. http://www.debian.org/Bugs/
GNUEmacs just started to use it as well, so fresh newcomers experience can be found on emacs-devel mailing list archive.
I also enjoy email integration in BTS, but I know it is a really non-trivial issue. MANY things can be learned from existing systems.

@Daniel: please link to the forum thread you'ra talking about.
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Hello, for the record:

branch :
http://www.redmine.org/repositories/browse/redmine/branches/work/mailing_lists

and i guess the forum thread is.. (?)
http://www.redmine.org/boards/1/topics/show/1435
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