On Fri, 18 Aug 2023 14:16:45 +0000 (UTC), it was noted on a mailing list related to email operations that the SPF
record for hotmail.com
had been changed, as well as that it did no longer contain include:spf.protection.outlook.com
, as it did before.
Before: v=spf1 ip4:157.55.9.128/25 include:spf.protection.outlook.com include:spf-a.outlook.com include:spf-b.outlook.com include:spf-a.hotmail.com include:_spf-ssg-b.microsoft.com include:_spf-ssg-c.microsoft.com ~all
After: v=spf1 ip4:157.55.9.128/25 include:spf-a.outlook.com include:spf-b.hotmail.com include:spf-b.outlook.com include:spf-a.hotmail.com include:_spf-ssg-b.microsoft.com include:_spf-ssg-c.microsoft.com -all
Not only did they remove that include:
, they also changed the policy from “~all” (softfail) to “-all” (hardfail), instructing others that honour the SPF
standard, to reject deliveries that are not authorized.
Microsoft did (and actually, still do) send a lot of email traffic over IPv6, however, with the removal of the include:spf.protection.outlook.com
mechanism for the SPF
record of hotmail.com
, it literally means that Microsoft removed ALL of their own IPv6 addresses from being authorized to send email on behalf of the hotmail.com
domain name.
As late as Thu, 31 Aug 2023 13:13:55 +0000 (UTC), they were still sending over their IPv6 addresses, although their new configuration doesn’t authorize this.
Since larger organisations (for example Microsoft, Google, … et cetera) usually distribute their outbound email deliveries over many different IPv6/IPv4 addresses, you may occasionally see that the deliveries are being tried from servers that their domain actually still authorizes.
The actual problem is with Microsoft/Hotmail, and their new configuration, and it will therefore be them you will need to poke for a solution.