If you use Amethyst, this article helps to make understanding the outbox model and the varying types of relays and their configurations easier to understand and implement. 
nostr:naddr1qq9hyetvv9uj6um9w36hqq3qgcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqxpqqqp65wjvcq4q