I'm going to go ahead and be pedantic: that format is not part of the SMTP spec. It's part of the Internet Message Format RFC (5322 in its latest incarnation),

I'm going to go ahead and be pedantic: that format is not part of the SMTP spec. It's part of the Internet Message Format RFC (5322 in its latest incarnation), which describes what's in the body of the email. The SMTP spec (RFC 5321) which describes what goes on the wire between an SMTP client and an SMTP server uses addresses in a '<to@example.com>' format.