The ebuild is using ${EDITOR} at build time, thus creating an implicit dependency on the ${EDITOR} package. It should use the new gentoo-editor script instead. See tracker bug 294651 for details.
Created attachment 237965 [details] new ebuild for package nmh This should also solve bug #262150 and, on my system at least, bug #323541
Please see http://bugs.gentoo.org/attachment.cgi?id=240761&action=view for another ebuild which includes the patch Giulio Bottazzi made plus the fix for Bug 319937.
nmh was removed from portage, therefore closing as wontfix for now. new ebuilds should go in bug 336057.