Whitelisting in OS X Server (pass greylisting without disabling it)
To whitelist domains from greylisting so mails from that domain arrive instantly, enter
sudo serveradmin settings mail:postfix:add_whitelist_domain = "example.com"
and replace example.com with the domain you intend to whitelist. It seems like you can also whitelist hostnames (server.example.com) and mail users (user@example.com), but I don't know how to do that yet, using:
mail:postfix:add_whitelist_host = _empty_array
mail:postfix:whitelist_from
OS X Server, 8GB, 2,93 GHz Intel Core 2 Duo