I'm a Technical Product Manager at Fortra (Agari) and we are having issues with
M365 SPF processing which is significantly impacting many customers who use our
hosted SPF service. This will also be a wider issue for many other senders.
We have noticed a change in behavior during M365 receipt where SPF records with
"exists" mechanisms are not being observed properly - causing rejections and
failed DMARC-SPF outcomes.
If I have an SPF record where an IP6 is defined before an "exists", SPF
authentication works OK.
"v=spf1 ip6:2a0d:7c40:3000:3d9::2 exists:%{i}._i.%{d}._d.espf.agari-dns.net
include:%{d}.fb.spf-protect.agari-dns.net -all"
<- 250 2.6.0
[email protected]<mailto:[email protected]>
[InternalId=35072702972535, Hostname=CWLP123MB4322.GBRP123.PROD.OUTLOOK.COM]
9514 bytes in 0.108, 86.011 KB/sec Queued mail for delivery
However, if an SPF record first lists an "exists", SPF fails to validate which
is not expected behaviour and other receivers do not have similar issues.
Eg:
v=spf1 exists:%{i}._i.%{d}._d.espf.agari-dns.net
include:%{d}.fb.spf-protect.agari-dns.net -all
-or-
v=spf1 exists:%{i}._i.%{d}._d.espf.agari-dns.net
include:%{d}.fb.spf-protect.agari-dns.net ip6:2a0d:7c40:3000:3d9::2 -all
<** 450 4.7.26 Service does not accept messages sent over IPv6
[2a0d:7c40:3000:3d9::2] unless they pass either SPF or DKIM validation (message
not signed) (S825). [CW2PEPF000056BD.GBRP265.PROD.OUTLOOK.COM
2025-02-06T09:40:07.649Z 08DD403C4BFB3BA6]
Really trying this mailop list as an avenue to get my voice heard by Microsoft
as I don't believe they are processing SPF correctly at the moment.
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
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