Mark Martinec posted a patch on January 27th to fix an incompatibility between amavisd-new-2.6.4 and MIME-tools-5.500 (full explanation in the URL). It seems we should either include the patch, or change the MIME-tools dependency to exclude the newer version. Older versions may also be affected (I haven't looked into it).
see also the linked bugreport in URL: <http://rt.cpan.org/Public/Bug/Display.html?id=65162 "For now, I'd recommend not using 5.500." MIME-tools is used by a number of packages: http://tinderbox.x86.dev.gentoo.org/misc/rindex/dev-perl/MIME-tools I probably should mask dev-perl/MIME-tools-5.500 and wait for a fixed release.
One can also use amavisd-new-2.7.0_pre14 (currently masked) which has in its RELEASE_NOTES: - ensure compatibility with a new version 5.500 of MIME-Tools,...
5.500 is gone. 5.501 is in the tree and fixes the problem. Thanks