The evolution 2.3.7 ebuild uses "dbus? ( <sys-apps/dbus-0.30 )" in RDEPEND, whilst evo builds and work just fine when using dbus3 (sys-apps/dbus-0.36_pre20050816 here) like it should, as all Gnome 2.12 components should be working fine with dbus3. Downgrading dbus to version 2 would break a lot of applications (HAL5 based ones as HAL5 requires dbus3 as an example) so that's not an option :-)
Thanks for reporting this. A new ebuild has been committed to resolve this.
*** Bug 103897 has been marked as a duplicate of this bug. ***