Hi, from our perspective the "450 4.7.26 Service does not accept messages sent over IPv6" message started intermittently a couple of month ago and it rather seems like some kind of temporar issue on the receiving side. Our IPv6 range is referenced through the include mechanism. This worked fine for many years - until a few month ago and affected all of our domains (several thousand and all with valid DKIM signatures).
blocking outgoing IPv6 smtp to 2a01:111::/32 was a quick "fix" for us - not pretty but arguing with MS seem useless. outgoing mail passes fine through IPv4 then: -A OUTPUT -d 2a01:111::/32 -p tcp -m state --state NEW -m tcp --dport 25 -j REJECT Am Thu, Feb 06, 2025 at 04:31:30PM +0000 schrieb Chris Spencer via mailop: > Hi Kirk, with the exists method we form A records as the underlying response. > We have an include available as a fallback option and we're investigating > migrating the spf.protection.outlook.com entries into the alternate include. > > Via an include the problem will go away as the IP6 will no longer form part > of the hostname which I suspect is the issue here. We've likely fallen foul > of permitted characters per rfc1035 although other receivers (eg Google) are > tolerating our IP6 entries within the exists. > > Chris. > > Chris Spencer (he/him) > Principal Technical Product Manager > +44 (0)118 228 0733 [cid:[email protected]] > fortra.com<https://www.fortra.com/> [cid:[email protected]] > meetcspencer<https://outlook.office.com/bookwithme/user/[email protected]?anonymous&ep=plink> > [Fortra]<https://www.fortra.com/> > > Fortra International Limited. Registered in England and Wales. > Registered number: 4172068. > Registered Office: 3rd Floor 1 Ashley Road, Altrincham, Cheshire, United > Kingdom, WA14 2DT > > > _______________________________________________ > mailop mailing list > [email protected] > https://list.mailop.org/listinfo/mailop _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
