OT: blacklisted email servers

[Mathew Newton]

In an increasing number of cases it very much does matter which outbound se rver you use though for a particular domain given the restrictions imposed by the enforcement of some domain's SPF/DKIM configurations.

For example, earlier this year Yahoo changed their DMARC policy to p=reje ct thus instructing recipient MTAs to reject mail received from servers not covered by Yahoo's SPF/DKIM declarations. Hence, mail sent from a Yahoo do main from any server other than Yahoo's can end up being dropped. The fact that you might be able to successfully authenticate with your ISP's mail se rver etc matters little - you really do need to use Yahoo's servers if you want to send mail that appears to come from a Yahoo address (this is proble matic in the context of mailing lists but that's one for another discussion ).

[The Natural Philosopher]

that makes no sense: It is not within Yahoos purlieu to affect the sending of mail by other relays.

[Adrian]

But it IS very much within Yahoo's purlieu to say publicly "We strongly recommend you only accept mail that says it's from our domains if it comes from one of these servers :"

[The Natural Philosopher]

Well yes, but that is not the same as saying 'we strongly recommend you bounce/drop/silently ignore mail that says it from yahoo, but comes from somewhere else, or mail from these servers that isn't given an envelope or from address of Yahoo'

And even if they do, they can't enforce it.

Yahoo can control what mail is sent from their relays and recieved by their servers. Beyond that its not their decision.

[Mathew Newton]

From an anti-spam/spoofing context it is arguably every domain's prerogativ e to decide who can send mail claiming to come from there. The corollary be ing though that they must accept the consequences of whatever mechanism is used to achieve this, not that Yahoo probably care about any collateral dam age caused.

[Mathew Newton]

Of course. But all anti-spam/spoofing mechanisms are enforced by the recipient MTAs and they are free to do what they like, including ignoring the SPF/DMARC policies of the sender domain which would be quite unusual.

[The Natural Philosopher]

That is not what he said. He said 'yahoo has stopped other people receiving mail stamped yahoo that doesn't come from their servers' They can't.

You are confusing the sender address, the envelope sending address and indeed the actual IP domain the mail is sent from. They are three different things. You can control relaying based on any or all of them, but you cant control someone elses relay.

If I try to send email to more than 4 yahoo targets blind copied, yahoo seems to silently dump it.

Gmail is similar. I regard them both as basically broken mail systems

[Mathew Newton]

Who said that? I didn't. I said that Yahoo has indicated through DMARC that other people *should* drop mail from Yahoo domains unless it passes the SP F/DKIM checks. As you say, they can't enforce it but no one is saying that can or even need to. The fact of the matter is that many mail systems are f ollowing Yahoo's recommendation.

[Mathew Newton]

You haven't recently enabled IPv6 have you? Quite a few are finding that, a t Google at least, mail carried over IPv6 is seemingly subject to more rest rictive checks than over IPv4. That said, the bar hasn't been set all that high (valid reverse PTR, SPF, etc) and you would usually receive a pointer to further information in a bounce.