Comcast was rejecting emails from my mailservers, complaining that they didn't have valid PTR records. But they do, so after messing around for at least an hour I realized my server was preferring ipv6. I tried the instructions at Forever Cached but that didn't do the trick. Set disable_ipv6 = true in /etc/exim4/conf.d/main/000_localmacros, restarted, and finally it seems to be working.
last updated 2013-05-10 19:45:52. served from tektonic.jcomeau.com