A few corrections to 822. RFC 2822, published in 2001, also known as 822bis. 822bis is more misleading than 822 in some areas, less misleading in others. It's easy to add syntax to a protocol. For most protocols, it's just as easy to remove syntax.
Mail is different.
A mail message lasts forever. Tomorrow's readers have to be compatible with yesterday's writers. If you're a new implementor, you'll be shocked at how badly 822 was designed.