so you can still know when someone has put you on their blocklist (which may
affect delivery), without using them.
also query dnsbls for our ips more often when we do more outgoing connections
for delivery: once every 100 messages, but at least 5 mins and at most 3 hours
since the previous check.
most content is in markdown files in website/, some is taken out of the repo
README and rfc/index.txt. a Go file generates html. static files are kept in a
separate repo due to size.
