From address doesn't meet the authentication requirements defined for the sender

[#1]

@PhilipHeyes 

Hosting has nothing to do with the current issues.  The move to Greenby (as currently planned) will have no impact on these issues.  This is all related to DNS configuration for plus.com (etc) which (under current plans) will be retained by Plusnet.

[#2]

@MisterW Aah, understood. Thankyo.

[#3]

@Townman 

".... if .... same email sent separately to the two addresses passes DKIM but when set as co-addressees fails DKIM then the issue must be with the receiving email services."

While I'm happy to accept that something may be misconfigured at Microsoft, note the "if" in your sentence.

We have evidence that emails sent to co-addressees fail DKIM, but has anyone tested that an email sent separately to a single addressee passes?  Or does it get through despite failing?

Either would be evidence of a problem, but it would help if we can nail down which of these two different possibilities it is.

@stuck has offered to ask his/her correspondents, but seems doubtful they'll be able to help.  What's needed is for someone who has both a PN email account and an MS account to try the experiment.  I'm sure there was someone on here recently who said they had both.  Send two identical emails, one with a single addressee and one with a co-addressee.  Compare the bounce and the headers of the one that gets through (assuming one does).  Does DKIM fail for one but pass for the other?  Or does it fail on both, but one gets through despite failing?

[#4]

I do not think it’s that simple.  I have (amongst others) outlook and Gmail email addresses.  I have co-sent to both and both got through.

in research elsewhere I have seen reports of the same email being given different SCL ratings by outlook and live.  I do not have a live account - I would suspect that the issue relates to sending to Microsoft co-addressees.

[#5]

@Townman 

Thanks, that's helpful, but you've still not answered my question.  Did the ones that got through pass DKIM?  Or did they still get through despite failing DKIM?

[#6]

I have no examples of SPF or DKIM failure, but mail is going to the outlook junk folder unless I have white listed the sender.

Test to Gmail / Google mail were delivered within 3 minutes - difficult to discern if that is normal or fast de-grey listing.

[#7]

If recipients are smart phone users I would estimate the probability of obtaining any e-mail headers as close to 0%.

[#8]

Just had an email fail

Final-recipient: rfc822; emailredacted
Diagnostic-Code: smtp; 550 5.7.515 Access denied, sending domain TEAMDB.PLUS.COM doesn't meet the required authentication level. The sender's domain in the 5322.From address doesn't meet the authentication requirements defined for the sender. To learn how to fix this see: https://go.microsoft.com/fwlink/p/?linkid=2319303 Spf= Pass , Dkim= Fail , DMARC= Pass [PR3PR08MB5804.eurprd08.prod.outlook.com 2025-07-03T11:09:17.321Z 08DDB9513D328929] [BN9PR03CA0665.namprd03.prod.outlook.com 2025-07-03T11:09:17.356Z 08DDBA19F5ABB7B0] [BN2PEPF00004FBC.namprd04.prod.outlook.com 2025-07-03T11:09:17.367Z 08DDB9121B27AADA]

headers are:

 Mail delivery failed: returning message to sender
Thu, 03 Jul 2025 12:09:17 +0100
0001
00000000
<>
dave@teamdb.plus.com
Thu, 03 Jul 2025 12:09:17 +0100
from [212.159.14.23] (helo=avasin-peh-003.plus.net) by inmx-peh-007.plus.net with esmtp (PlusNet MXCore v2.00) id 1uXHob-0009kB-L9 for dave@teamdb.plus.com; Thu, 03 Jul 2025 12:09:17 +0100
from avasout-ptp-001.plus.net ([192.168.2.6]) by Plusnet Cloudmark Gateway with ESMTP id XHobu2ctU8CLOXHobup8TK; Thu, 03 Jul 2025 12:09:17 +0100
100.00
v=2.4 cv=BMUQr0QG c=1 sm=1 tr=0 ts=686664dd cx=a_idp_d p=QhnmdGnfZl10ibMM-eB4:22 a=fTP+3eAQz1Npw2x2rIHg1Q==:117 a=JpQFdOCcWwLefhrs:21 a=HpEJnUlJZJkA:10 a=r77TgQKjGQsHNAKrUKIA:9 a=69EAbJreAAAA:8 a=ZJBQcd3GU851oevA_6MA:9 a=QEXdDO2ut3YA:10 a=-nLOOE-jNnsA:10 a=yMhMjlubAAAA:8 a=EBOSESyhAAAA:8 a=UqCG9HQmAAAA:8 a=C4W0dgAsntGCo1o8qSsA:9 a=f7g3CFGLjmAxJFOoyGbZT193Uiw=:19 a=ZXulRonScM0A:10 a=zZCYzV9kfG8A:10 a=GBxa4UyLAAAA:8 a=BrDiTsk0AAAA:8 a=m0z7Jb8Ya3_BLVq6aX4A:9 a=G7Lve7jeAAAA:8 a=oCcaPWc0AAAA:8 a=VpAwWidu-gCG43BqYsEA:9 a=3ZKOabzyN94A:10 a=4d2D4LtiAAAA:8 a=VaVsUSfoZ_ruBbcr4yMA:9 a=s6KZz1zF_Zfl3LP4:21 a=UiCQ7L4-1S4A:10 a=_W_S_7VecoQA:10 a=lqcHg5cX4UMA:10 a=I-7ugS_TDPP3PmrZALkA:9 a=KQqxNPgzF0kA:10 a=VEiTNn8F7TgA:10 a=yJM6EZoI5SlJf8ks9Ge_:22 a=y65l9bsv7i_rySDlTQ9X:22 a=6S1Z7LM3JzRR8jR6zzph:22 a=7GnO-AvVFhA1zpJMnGM7:22 a=rpXtYnK6aTl2ddkKRDiu:22 a=ZzlsgNkTd4aLiCgO_Y1T:22 a=hn0sSy4U25RWEgiCHr5y:22 a=HhbK4dLum7pmb74im6QT:22 a=p-dnK0njbqwfn1k4-x12:22 a=3lMFb2gA92Fu04n3_66V:22 a=NWVoK91CQySWRX1oVYDe:22
1.0
multipart/report; boundary="------------I305M09060309060P_911717515409570"
MS4xfHL2nJeX1Ak/Vp/Pl49V1at1+nDEzfoJTpxErrTZ4l14jh4/m76w4zz1VndP7ZEPHHUM8e3bGLuloWHIOvxHl6xewzTEW4ZFvAJUb4wY+02Gb2q+gPRV gXS/q+XLac3r3Zdiwsw2qg0hQ6j8jFA6SqbmIuLk9OFrSQQjsaCJY8pb
" Spam 99
by PlusNet MXCore (v5.00)
by PlusNet MXCore (v5.00

[#9]

---

@Tim-J wrote:

@stuck has offered to ask his/her correspondents, but seems doubtful they'll be able to help..

---

I'm afraid that is so, sorry.

Mind, having apologised for not being able to help, surely that sort of testing is something PM should be doing in order to be able to fix things if they can, or gripe to MS about if it's beyond their control.

[#10]

Not when things appear to be working for the majority.  To investigate an issue, one needs an assured means of reproducing the problem or evidence from the occurrences which have been encountered.

[#11]

Message to single hotmail recipient blocked:

The response from the remote server was:
550 5.7.515 Access denied, sending domain XXXXXX.PLUS.COM doesn't meet the required authentication level. The sender's domain in the 5322.From address doesn't meet the authentication requirements defined for the sender. To learn how to fix this see: https://go.microsoft.com/fwlink/p/?linkid=2319303 Spf= Pass , Dkim= Fail , DMARC= Fail [AS8PR07MB7398.eurprd07.prod.outlook.com 2025-07-04T17:28:56.238Z 08DDB91EC6D73843] [PAZP264CA0090.FRAP264.PROD.OUTLOOK.COM 2025-07-04T17:28:56.243Z 08DDBAA17D9FCBC6] [AM4PEPF00025F96.EURPRD83.prod.outlook.com 2025-07-04T17:28:56.252Z 08DDB599ED619FB2]

I should add that this is being sent through a gmail smtp server as we don't have plus.net as our broadband supplier, so cant use the pjus.net smtp server. However, this has worked fine until this recent problem appeared a few weeks ago.

[#12]

@FF101 

should add that this is being sent through a gmail smtp server 

That's not going to work, the SPF record will only set the Plusnet servers as permitted senders. If you have a Plusnet email account then you should be able to use the Plusnet SMTP server. You will need to authenticate with your email account and password

[#13]

It certainly has worked until recently and still works fine with non MS recipients.

Unfortunately for some years now plusnet has not allowed its smtp server to be used by former customers who have no ongoing contract, unless using a Plusnet broadband connection.

Hopefully the Greenby email transfer will at least avoid this issue ?

[#14]

@FF101 

Well that explains entirely why it’s not working.  Email sent FROM a Plusnet email address should only be sent via Plusnet SMTP servers.  The fact that you do not use Plusnet as your ISP does not preclude you from using their SMTP server.

The consequences of Microsoft’s draconian measures had brought about the addition of SPF for @*.plus.com which affirms that only Plusnet’s SMTP servers are legitimate MX servers for sending emails on behalf of these addresses.

The fact that this used to work via Gmail’ SMTP servers is the very act which Microsoft has sought to close down.

Change your outgoing server to relay.plus.net and use the same credentials as the incoming server.

[#15]

Unfortunately for some years now plusnet has not allowed its smtp server to be used by former customers who have no ongoing

that was the case until a year or so ago, when access to the SMTP servers was permitted for anyone with a Plusnet mail account