Just a quick idea while I think about it. Some days ago a friend of mine recieved a bounce from AOL mail daemon because for some reason the mail list had been blackholed or something long story but... The pages at http://postmaster.info.aol.com/ contain reference to a DUL list, this would stop an e-smith mail daemon from sending mail into the AOL domain (and probably others we are not yet aware of). So my idea is to interpret the error code returned by the daemon and maybe use a smarthost setup to fallback to. Is this already implemented and Ive missed it? Where would I start?
