Mailservers drop mail on the floor because they are doing spam-filtering AFTER accepting mail for final delivery. Once it's been accepted for final delivery, it can no longer be rejected.
The delivery server doesn't generate the bounce message you were expecting; that's generated by your own mailserver, on seeing a REJECT status code from the delivery server.
Mailservers do spam-filtering after accepting for final delivery because spam filtering can be processor-intensive. Sometimes it's farmed-out to an appliance or whatever. To have the SMTP process suspended while Spamassassin goes through it's contortions multiplies the consumption of server resources on the SMTP server.
The delivery server CAN'T (and shouldn't) send you the desired bounce message, because it doesn't really know who you are. It can't rely on the From: address, because you could be sending on behalf of someone else.
In my view (and the view of the RFCs), if a server says "200 OK Accepted for final delivery", then it MUST deliver the message.
There's an awful lot of the kind of server-side spam-filtering that does actually involve delivering: the kind that filters mail into the recipient's spam folder. That mail hasn't been dropped on the floor. It's been delivered, just not to the inbox.
I'm willing to stipulate that this is correct and would, in my case, be a difficult problem to solve.
But nobody is losing job offers or missing kids' schedules or breaking their summer plans because of my mailserver.
I am talking about gmail. I am talking about MS (whatever it is). I am talking about yahoo.com.
Their spam heuristics are, in many cases, laughably bad - they are demonstrably, clearly broken. If I email my wife twice daily for 15 years and then one of my responses to her emails gets put in the gmail spam folder ... what words to even use for that ?
They need to fix this. I don't care how sticky of a problem it is.
$employer uses MS for email hosting. MS recently started dumping every single email from every single Apache mailing list in the spam folder. These are mailing lists to which I've been subscribed for a decade, to which I regularly send emails, and which probably have thousands of subscribers. There is no option for me to whitelist the mailing list, only individual senders, of which there are hundreds.
Everything about megacorp spam filtering is broken.
Well, gmail, MS and Yahoo have their own ideas about what "broken" means. Google in particular forces changes to standards by simply implementing them in their own services. Those changes never make it easier for small-fry postmasters; so I conclude that Google would like all small-fry mailservers to disappear.
Discrimation through spam-filtering isn't unthinkable, and it would be hard to prove (especially if they claimed there was "AI" involved in the filters). Google used to have really good spam filtering; I can only suppose that the reason it's got worse is that they want it worse.
if gmail wanted to, they could provide some SMTP extension. eg. they could advertise that the sender server can send a callback url where gmail will post back the results
there's already some kind of feedback loop mechanism, but mostly available for large senders.
The delivery server doesn't generate the bounce message you were expecting; that's generated by your own mailserver, on seeing a REJECT status code from the delivery server.
Mailservers do spam-filtering after accepting for final delivery because spam filtering can be processor-intensive. Sometimes it's farmed-out to an appliance or whatever. To have the SMTP process suspended while Spamassassin goes through it's contortions multiplies the consumption of server resources on the SMTP server.
The delivery server CAN'T (and shouldn't) send you the desired bounce message, because it doesn't really know who you are. It can't rely on the From: address, because you could be sending on behalf of someone else.
In my view (and the view of the RFCs), if a server says "200 OK Accepted for final delivery", then it MUST deliver the message.
There's an awful lot of the kind of server-side spam-filtering that does actually involve delivering: the kind that filters mail into the recipient's spam folder. That mail hasn't been dropped on the floor. It's been delivered, just not to the inbox.