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Indeed but what's the purpose of that. The SMTP server knows the IP address anyway and can DNS lookup if needed. The one chatting with server can say hello foll
by srean 6y ago
Indeed but what's the purpose of that. The SMTP server knows the IP address anyway and can DNS lookup if needed. The one chatting with server can say hello followed by any arbitrary string
- ink_13 6y ago> can DNS lookup if needed Can it? Not every machine that sends mail is on the public Internet.
- quesera 6y agoSMTP (1982) predates DNS (1985). Reverse DNS was added to SMTP servers as an anti-spam feature about 15 years after HELO was established. But to be honest, I'm not sure HELO was ever really useful. In the very early years, it might have been appropriate to reject messages where the MAIL-FROM domain did not match the HELO domain. Not for long though.
- albertgoeswoof 6y agoThis is the crazy thing about email, it's ancient, 39 years old. I bet it'll still be around in 20 years from today.
- srean 6y agoAh! That was the missing information. Thanks, now it makes sense
- megous 6y agoHELO is not really used that much anymore. It's EHLO now. And response to it includes capabilities of the server. So it serves negotiation of those at the beginning of the session, too. It's better to be prompted for those, instead of just sending them unannounced, in case client just want to switch to TLS first via starttls.