We use Office365 for hosting mail. You may stop reading now, no offense taken. :-) Recently and intermittently, emails from the centos and centos-devel mailing lists are being put in my "Junk E-Mail" folder by Microsoft (not by any client filtering). My insightful email admin has been working with Microsoft to nail down the cause and it is (partly?) due to centos.org not having a DMARC DNS record. I verified this is true with a missing "ANSWER SECTION" if DNS is queried: dig _dmarc.centos.org txt When I pressed for more details about the intermittent filtering, he replied: "Maybe passing SPF or DKIM for some sending domains helps get some of them through? I can’t be totally sure in this evolving Microsoft dynamic situation. But I’m still not through with them. Still asking questions trying to draw out answers..." Microsoft suggested: You can ask an admin in the sending domain to configure their email authentication records: https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/email-validation-and-authentication?view=o365-worldwide#ask-the-sender-to-configure-email-authentication-for-domains-you-dont-own My apologies if this is bringing up issues already beaten to death. But if it could be addressed without too much hassle...it might help others as well. Thanks!