[ih] Ancient mail question about 551 and 251 reply codes

[John Levine]

For a very long time SMTP has had the 251 and 551 reply codes which
say that the recipient is somewhere else and give the new address. 251
means the reciving system accepts the message and will presumably
forward it, while 551 rejects the message so you're supposed to resend
it yourself. They were introduced in a different form in RFC772 in
1980 and in the current form in RFC780 in 1981.

My question is whether anyone has actually done anything with these,
like resend the message to the new address, or update address books,
or at least report the reply to the sender somehow. I don't ever
recall it, but in 1980 I was still on uucp.

R's,
John, uucp at computer.org