amavisd-new used to have a stable ppc ebuild, but as the new version have come out, it has only been marked ~ppc. This is interesting since it is also marked stable on ppc64. I have sucessfully built and am using on a decently busy server amavisd-new-2.3.3-r2. Please consider marking this stable on ppc.
Marked ppc stable, thanks for the report.
Closing. :p