> On 21 Oct 2020, at 09:41, Renaud Allard via mailop <mailop@mailop.org> wrote: > > > > On 10/20/20 12:41 PM, Daniele Rossi via mailop wrote: >> Hi, >> we try to send to Microsoft Account and we receive this message: >> *Queued mail for delivery -> 250 2.1.5* >> The problem is that the mail does not arrive either in spam or in the inbox. >> This happens for most of our ip's. >> Can anyone explain this abnormal behavior to me? > > This should never happen and is a proof that the infrastucture doesn't > respect good email practices. This mostly happens with _free_ MS customers, > generally not with paid ones. But I guess you get what you paid for.
Microsoft has always silently dropped mail on the floor when it judges that to be the right thing to do. It’s an issue and I personally believe it’s bad practice. But I’m pretty sure that Microsoft have their reasons and have decided it’s effective. It is more common on the free mail side of things, however, it can happen on the paid side as well. In that case, Microsoft is giving the mail a BCL score and the O365 tenant is instructing MS to delete the mail if the BCL reaches a certain threshold. I vaguely remember a discussion somewhere (either here or the IETF DMARC list) a few months ago about how MS is also just discarding mail that fails DMARC when the sender has a p=reject record. They’re doing this after the fact because their system is handling DMARC after the SMTP transaction and they don’t want to be adding to backscatter. laura -- Having an Email Crisis? We can help! 800 823-9674 Laura Atkins Word to the Wise la...@wordtothewise.com (650) 437-0741 Email Delivery Blog: https://wordtothewise.com/blog
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