On 2026-02-08 at 18:56 -0500, Doug wrote: > As a side note, I wish I lived in a world where mail servers were denied > from sending emails to servers they block. I get that this is > infeasible, that's why I said "I wish". It's just not fair that they can > basically defame me by making it look like I'm not responsive when, > really, they don't check to see if they are sending to a recipient that > they themselves have blocked.
I disagree. There is (some) value in receiving email even if you can't send back to it. For example, receiving a verification code so that you can log into a platform to e.g. change your email address. Or as mentioned by Miliotis, just receiving bills¹ and other one-way communications. (those are probably using an ESP, though) Even if they implemented that, this would probably not show up here, since they are not blocking vought.co, but "only" one of the IP addresses you use o send them email, and that won't show until htey really receive your reply. What I would be eager to see is that, if [email protected] sent an email to [email protected], a reply from Bob to that message should be able to get through to Alice (ideally to the Inbox, even). Even more so for these "I dislike your neighbors" blocks. As an algorithm description: * IF the incoming email has an In-reply-to header, and * there is an email with that Message-id in the receiving mailbox, and * it was sent by the mailbox owner, and * it was sent less than $RECENT days ago, and * the incoming email From: is amongst the recipients for that previous email, and * that From value is valid per DMARC rules (i.e. SPF/DKIM passes), and * that sender is not explicitly blocked be the recipient, and * no more than $COUNT replies to that email were received THEN this is a reply to what your user had sent, so allow it to get through. It is impolite to block the replies to the emails your users send. If your customer sent an email, there is an expectation that a reply /will/ be desired as well. There is an implicit requisite that Message-id are not predictable. But a system where Message-ids could be guessed would be vulnerable to malicious emails getting into existing threads, so it should already be that way (and what everyone? is doing), so this doesn't impose any extra work. Regards ¹ Much as I would enjoy reading a story on how you didn't need to pay the electricity bill because they failed to deliver it to you because Microsoft silently blocked it, or even to that Microsoft had to pay for it... that'd likely be much more problematic. _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
