Hi, I got a report from a user that said he received a bounce from postgrey.
  neptune.psmail.net is the outgoing server that received the 450 from postgrey, reported a 554 to
the human as undeliverable, and then continued to retry and successfully deliver the mail.

I've added /\.psmail\.net$/ to my whitelist.local, but thought other people might care about it. I
don't know if only adding neptune is better (perhaps neptune is outgoing and the others are for
incoming?)

host -t mx psmail.net
psmail.net mail is handled by 5 venus.psmail.net.
psmail.net mail is handled by 7 mars.psmail.net.
psmail.net mail is handled by 9 jupiter.psmail.net.
psmail.net mail is handled by 3 uranus.psmail.net.