>> I'll argue that whichever it is, it is also a mis-feature.
>
> Right. The "problem" is in the way how signing is implemented in the
> transport (redirecting the SMTP DATA output stream to an extra fd).
> While it would be possible to chain both functions, performance would
> really suffer. I'd need to merge both functions and calculate both
> hashes at the same time. I can't promise any progress before end of
> next week though.
>
>> Besides presenting a use-case and rationale, as I've just done, what can
>> I do to help?
>
> Play the guinea pig with a tarball that I'll send over. :)
OK, it took me a bit longer. I've put code in CVS that enables
concurrent Domainkeys and DKIM signing. Here's a snapshot tarball:
http://duncanthrax.net/exim-experimental/exim-cvssnap-2008-03-05.tar.gz
/tom