John Leslie wrote: [...] > Let's also leave aside the religious arguments about what belongs > in 2821bis. (IMHO, this is largely an operational tuning issue, and > the protocol spec shouldn't try to mandate operational tuning.) [...]
> Backscatter is a support nightmare. Unless you can match NDNs to > actual messages sent, many customers will be happiest if you discard > them all. But "discard them all" is against my religion. Professions have their rules, lawyers don't work for the mob, docs don't help with euthanasia, hackers don't manipulate data, soldiers don't attack civilians, and postmasters don't "discard them all". The same customers could whine if their mail with a typo caused a good bounce ending up in /dev/discard_them_all. For one of the religions you don't wish to talk about it is a core dogma to cause good bounces in a rare scenario decreed to be legit in a closely related religion you also don't wish to talk about. On the SMTP list we IMO cannot say that the future SMTP standard is (only) a religion. It is supposed to be the real thing, replace 821 in STD 10 in about 30 months. > The problem <ietf-smtp> can't seem to face is that the mere > presence of a process listening on port 25 of a particular IP > address says nothing about intent to receive email for a particular > domain which has an A)ddress record pointing to that IP address. An > MX record _does_ state such an intent. 2821 and 2821bis have it clear that the mere presence of a listening process does not say anything about the intent to receive mail for the corresponding domains. The MX can say something else, without MX a listening process at A or AAAA can reject clients or individual mails as it sees fit. The problematic situation is the absence of MX and listening process, senders are forced to wait 100 hours, somebody might find the reboot button of the affected host. Another problematic situation is mail claiming to be "from" this domain without MX, receivers cannot wait until somebody finds the reboot button for a quick plausibility test, they are forced to reject such suspicious mails temporarily. Religious operational tuning or not, when receivers accept suspicious mails "on probation" they didn't read and understand 2821bis, likely following their own homebrewn "discard them all" strategies. Frank
