Hotmail rejecting mail from PN [Diagnostic-Code: smtp; 550 5.7.1]

[#1]

In the above post I suspect @PhilipHeyes failed to consider/read:

"DMARC Missing: PlusNet reportedly lacks proper DMARC entries, leading to stricter filtering by Microsoft."

I suspect if PlusNet had correct DMARC information Microsoft would be less likely to block PlusNet servers.

Either way after over a month this issue should have been fixed weeks ago!

[#2]

I speculate you attempt to re-write my post 🐵

Not a month, more like 9 months of issues with delivery to Microsoft and for a range of distinct reasons.

The current blocked email servers situation occurs after repeated spam sending events from the Plusnet SMTP server.
The last such event was only a few weeks ago, I had the 'Boots' spam message from 4 different Plusnet domains in one day.

DMARC: Look at how say Gmail score the DMARC of an inbound email sent via a Plusnet SMTP server.
Every time we see DMARC=Pass meaning the Plusnet DMARC DNS settings are a valid entry.

[#3]

I have never experienced these reported, recent Spam email messages. I know I am on the PN "High Touch" network (now reportedly in a minority) I was just wonder if this has any bearing on differences in people's experiences? Not that it necessarily helps...

[#4]

Apologies if I am merely repeating/reinforcing what has been said over the past few weeks but, yet again, my attempt to send an email to a relative using Hotmail has been rejected with the following message :~

Diagnostic-Code: smtp; 550 5.7.1

Unfortunately, messages from [212.159.14.20] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3140). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [Name=Protocol Filter Agent][AGT=PFA][MxId=11BCF349138FA8A7] [DB3PEPF0000885B.eurprd02.prod.outlook.com 2026-03-12T15:37:41.275Z 08DE79A4958DD2BD]

Is there any  progress towards resolving the issue?

[#5]

Just do what I’ve done and set up your own Hotmail/Outlook email. Works fine. 

[#6]

---

@dgp wrote:

...set up your own Hotmail/Outlook email. Works fine. 

---

Except it wouldn't "work fine" if, like many people here, you have created numerous mailboxes and/or aliases for those mailboxes.

[#7]

Perhaps when all the mail boxes have migrated to Greenby the open relay situation of relay.plus.net:25 from Plusnet IPs
will finally be slammed closed, it is an utterly shameful situation that should have been resolved over a decade ago to prevent the continuing reputational damage of spam senders being suffered by all customers.

Only in recent weeks was there a spam sending event that came from 4 different <domain>.plus.com accounts on one day,
how hard can it be to terminate this scourge ?

[#8]

The problems sending to Hotmail addresses continues:

Final-recipient: rfc822; <redacted>@hotmail.co.uk
Diagnostic-Code: smtp; 550 5.7.1 Unfortunately, messages from [84.93.230.227] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [Name=Protocol Filter Agent][AGT=PFA][MxId=11BD09A2D1ECF819] [AMS1EPF00000093.eurprd05.prod.outlook.com 2026-03-18T10:32:27.888Z 08DE84D1690C6E3F]

[#9]

The most recent spam sending breach was yesterday. TV Licence Renewal scams sent from two different <domain>.plus.net customer accounts.

Would it be wishful thinking to hope when relay.plus.net is migrated to Greenby it will no longer be available as an open relay and it will be served by a different set of IPs that might not be blocked for spam sending ?

[#10]

Recently was migrated to Greenby.

Emails to an Outlook address are being bounced because you, PlusNet aka Greenby, are on Microsoft Outlook's Block List. 

Reporting-MTA: dns; avasout-ptp-002 [84.93.230.235]
Received-From-MTA: dns; [192.168.1.206] [51.7.143.32]
Arrival-Date: Tue, 17 Mar 2026 22:05:38 +0000


Final-recipient: rfc822; [Removed]@outlook.com
Diagnostic-Code: smtp; 550 5.7.1 Unfortunately, messages from [84.93.230.235] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [Name=Protocol Filter Agent][AGT=PFA][MxId=11BD01C756C47136] [BL6PEPF0001AB75.namprd02.prod.outlook.com 2026-03-17T22:05:38.957Z 08DE80E3AFA94B05]

Last-attempt-Date: Tue, 17 Mar 2026 22:05:39 +0000

I'm not interested in technobabble. It needs to be fixed. Clearly everybody is aware of this because it's been going on for some months if not years, so there's no excuse - especially now that Greenby have a permanent interest in providing the Plusnet email service. Shall I hold my breath? Probably not. 

Moderator's note by Mike (Mav): Personal information removed from a public forum (to an area that staff can see).

[#11]

Seems it's not just Plusnet/Greenby having email issues?

Microsoft Domain Blacklist Causes Email Problems for UK ISP Zen Internet

https://www.ispreview.co.uk/index.php/2026/03/microsoft-domain-blacklist-causes-email-problems-for-u...

"Customers of broadband ISP Zen Internet appear to have been experiencing difficulties sending emails to Microsoft’s popular email services (Outlook / Hotmail etc.) since last week, which occurred after the software giant “blacklisted some domain servers hosted in our network“."

[#12]

Outlook/Hotmall are very enthusiastic when marking emails as spam. I can only assume if people don't log into their Outlook/Hotmail account and say otherwise it eventually results in the behaviour we are seeing.

[#13]

I have been adding all the required information to ticket 252894860 for the past few weeks and have just added another 7 or 8, I have been trying to send an email to <name>@hotmail.de for the past hour, all attempts have been bounced.

This should have been sorted weeks ago, why has it not been?

[#14]

@red-ray wrote:
This should have been sorted weeks ago, why has it not been?

Perhaps because neither Plusnet nor Greenby are devoting enough resources to sorting out problems in an email service sold and bought on the cheap?

[#15]

I have just tried to send an email to Greenby on the above issue ~ and at what I thought was the correct address, but it has been bounced back. Am I using the wrong address ?

Your message did not reach some or all of the intended recipients.

      Subject:     Bounce back of emails to Hotmail account holders

      Sent:  20/03/2026 12:37

The following recipient(s) cannot be reached:

      'complaints@greenby.com.' on 20/03/2026 12:37

            Server error: '550 <complaints@greenby.com.> invalid address 'complaints@greenby.com.''