There's a reason that sendmail exists, and that the sendmail book was so gigantic. Because it was terrible software, yes, but also because it was routing mail a

There's a reason that sendmail exists, and that the sendmail book was so gigantic. Because it was terrible software, yes, but also because it was routing mail across a variety of different systems with different addressing rules and what have you. RFC 822 didn't just come into existence one day.