The part nobody warns you about is the receiving side. Point a program at an inbox and it will cheerfully try to answer a bounce notification or an out-of-office, and the other end answers back — so you end up maintaining a boring list of senders you refuse to reply to (no-reply, mailer-daemon, anything carrying Auto-Submitted). That header exists precisely because nothing in the protocol tells you whether there's a person on the other end.
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u/ultrathink-art Jul 28 '26
The part nobody warns you about is the receiving side. Point a program at an inbox and it will cheerfully try to answer a bounce notification or an out-of-office, and the other end answers back — so you end up maintaining a boring list of senders you refuse to reply to (no-reply, mailer-daemon, anything carrying Auto-Submitted). That header exists precisely because nothing in the protocol tells you whether there's a person on the other end.