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

[#1]

I have twice pasted the X- material and it just vanishes.

So now I am trying for the 4th time with the same info in a PDF attachment
having had a .txt file rejected.

[#2]

Old joke.

In some cases Outlook used to be referred to as Outhouse. (The polite terminology for external toileting facilities)

[#3]

---

@Townman wrote:

Probably stuck in the spam filter ... one of the mods will unblock it shortly!

---

It's a new day and neither of my attempts to reply to you yesterday have been unblocked.  I note that @PhilipHeyes has also mentioned a disappearing post.

Is it really an over active spam filter, or is it that using the </> tags triggers the disappearance?

[#4]

May it be the case that plus.com needs to enable a DMARC policy?

More Information About Dmarc Policy Not Enabled

This Warning indicates that the DMARC record for this domain is not currently protected against phishing and spoofing threats. To resolve this Warning you will need to set a Quarantine or Reject policy on the domain's DMARC record. Setting a Quarantine or Reject value will prevent fraudsters from spoofing the domain as mail servers will Quarantine or Reject messages that fail authentication tests.

[#5]

I thought the same, but I guess the domain is " plus.com", i.e. it likely does send >5k emails a day.

[#6]

@jkg You thought the same as who?

[#7]

Stuck

[#8]

I tried to e-mail three addresses on one e-mail, one of which was a Hotmail account. The Hotmail account bounced the e-mail back to me, the others received the e-mail. This ties in with earlier posts in this thread, however the next stage is interesting......

I then forwarded the originally sent e-mail to the Hotmail account, this too was bounced back to me. I thought that this is strange as I can send e-mails to just a Hotmail account. This suggests that something in Microsoft's filtering is "looking" at the whole content of the e-mail and detecting that further down the forwarded e-mail there is the original e-mail with several recipients, one of which is the Hotmail account.

I am using a Window 11 PC and Outlook 365. All software is up to date.

[#9]

We sent a business email this morning to 3 recipients of which one was a Microsoft a/c xxxxx@live.com
and the Microsoft live.com is the only one that has ben rejected with  :-

Spf= Pass , Dkim= Fail , DMARC= Pass

Attached as a PDF are the rejection messages.

I've redacted as needed, the single PDF contains all lines from the two rejection error files.

[#10]

@ebforum said "I then forwarded the originally sent e-mail to the Hotmail account, this too was bounced back to me. I thought that this is strange as I can send e-mails to just a Hotmail account."

With seemingly random pass/fail results like this, I continue to think that MS is operating a scoring system, presumably paying special attention to senders via plus.com which it has decided is a high volume sender.

But did DKIM fail on both your attempts?

[#11]

@Tim-J , this is what was returned:

SMTP error from remote mail server after end of data:

    550 5.7.515 Access denied, sending domain xxxxx.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= Fail , Dkim= Pass , DMARC= Pass [AM8P195MB1025.EURP195.PROD.OUTLOOK.COM 2025-07-17T06:57:50.620Z 08DDC492C73A40F2] [DU2PR04CA0089.eurprd04.prod.outlook.com 2025-07-17T06:57:50.653Z 08DDC4BD2B0DF9E0] [truncated]

[#12]

DKIM pass but SPF fail. Curiouser and curiouser, said Alice.

[#13]

Is this also SPF related ?

Sent this morning this email failure occurred to a single recipient at a  talktalk.net email address,
it is odd because 84.93.230.244 is present in : _spf-internal.plus.net    


Reporting-MTA: dns; avasout-ptp-003 [84.93.230.244]
Received-From-MTA: dns; xxxxxlaptop [86.30.96.254]
Arrival-Date: Fri, 18 Jul 2025 10:23:53 +0100


Final-recipient: rfc822; xxxxxxxxxxxxxxxxx@talktalk.net
Diagnostic-Code: smtp; 550 5.7.1 Connection refused - [84.93.230.244] blocked by Validity - https://senderscore.org/blocklist-lookup/ - OXSEU001_102 - https://postmaster-oxseu.vadesecure.com/inbound_error_codes/#_102

Last-attempt-Date: Fri, 18 Jul 2025 10:23:53 +0100

[#14]

@PhilipHeyes 

Thank you for those precise diagnostics - I have flagged them to the team.

[#15]

Historically I have seen/experienced inconsistencies between servers on the AWS platform.