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

[#1]

The blockade continues.

Reporting-MTA: dns; avasout-peh-002 [212.159.14.18]
Received-From-MTA: dns; [192.168.0.18] [86.30.96.254]
Arrival-Date: Fri, 06 Feb 2026 14:38:08 +0000


Final-recipient: rfc822; rxxxxxx7@hotmail.com
Diagnostic-Code: smtp; 550 5.7.1 Unfortunately, messages from [212.159.14.18] 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=11BCC89E671C6321] [DB1PEPF000509F4.eurprd02.prod.outlook.com 2026-02-06T14:38:08.303Z 08DE644F35DB95B3]

Last-attempt-Date: Fri, 06 Feb 2026 14:38:08 +0000

[#2]

@plusnettony 

Yes, @PhilipHeyes is correct.  The problem with server 212.159.14.nn continues...

This bounce just in from a @hotmail.co.uk address:

Diagnostic-Code: smtp; 550 5.7.1 Unfortunately, messages from [212.159.14.17] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3140).

:deepsigh:

[#3]

@plusnettony 

We are still getting bounces, even from a mail sent to a single person. Yesterday morning a lady known to a number of our dancers passed away. The husband asked us to let people who they knew them about the sad news.

It's this sort of communication, amongst others, we are often asked to forward because we have a lot of contact details, Obviously we are going to keep those details secure and confidential, which means using a distribution list with BCC.

This time we sent individual emails to a few people but we have still had a bounce from a hotmail address, please see below:-

 >>>>>>>>>>>>>>>>

Reporting-MTA: dns; avasout-peh-004 [212.159.14.20]
Received-From-MTA: dns; smtpclient.apple [212.159.87.235]
Arrival-Date: Fri, 06 Feb 2026 21:56:55 +0000

Final-recipient: rfc822; ************@hotmail.com
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=11BCC199723C98A1] [BN3PEPF0000B072.namprd04.prod.outlook.com 2026-02-06T21:56:56.325Z 08DE60CCBF6DAB9D]

Last-attempt-Date: Fri, 06 Feb 2026 21:56:56 +0000

 >>>>>>>>>>>>>>>>

In the ticket I rasied with Plusnet CS I had the following response from a CSC Analyst....

 >>>>>>>>>>>>>>>>

*************** - CSC Analyst

3:42pm, Friday 30 Jan 2026

Dear 

I have reviewed this as part of the HLE intervention role.

Email address: *************@ourdomain.co.uk

The email on the task is wrong, but i have asked our network team to look into the correct email address.

They can see emails being sent but nothing blocked on our side, all they can see are a lot of bounce backs.

I have checked your IP address and it is not the cause of the bounced messages.

I can confirm that having multiple emails in the to or CC fields can cause issues but having 10 or less will be fine. If you have a list is may be worth splitting it up and sending x per hour instead of all at the same time.

You can call us on ***************  between 8am and 8pm seven days a week.

Kind regards,

 >>>>>>>>>>>>>>>>

This not true them problem is not with the number of emails. The problem is somewhere else!

[#4]

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@Lordwotsit wrote:

This not true them problem is not with the number of emails. The problem is somewhere else!

---

Correct - the problem is Microsoft.

[#5]

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@jab1 wrote:

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@Lordwotsit wrote:

This not true them problem is not with the number of emails. The problem is somewhere else!

---

Correct - the problem is Microsoft.

---

Hi John,

Oh, okay. Why is that?

I didn't used to get these problems. What has changed to cause various emails, single or in a dist-list, to be treated as blacklisted mail?

[#6]

@Lordwotsit I'm no expert on this, but all the 'Microsoft' email brands appear to be exhibiting the same, or very similar, behaviours - why, only they can tell you, and they won't.

[#7]

@Lordwotsit are you sending from native <account>.plus.com or a domain address ? 

If its the latter, do you have the correct SPF record setup ?

[#8]

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@MisterW wrote:

@Lordwotsit are you sending from native <account>.plus.com or a domain address ? 

If its the latter, do you have the correct SPF record setup ?

---

I'm sending it using the domain address, that's supposed to be linked via plusnet. Which I was told a long, long time ago(2005) would make no difference to my sending emails. Nobody has told me anything to the contrary since.

We did have a problem in 2023 with Gmail and @Townman helped me get the right information into an "Additional DNS records (Advanced)"   See attached.

Is this what you mean or am I missing something else?

[#9]

@MisterW 

I use an external domain for my emails, with DNS provided by netnerd. I've got a correctly configured SPF, DKIM and  DMARC 

I route through relay,plus.net for outgoing email and the sender email address is valid (i.e. can be responded to) and I get rejections from MS because the PN server sending the email is blacklisted by MS

So I guess what is happening is that PN request the address of the PN Email server is taken off the MS blacklist and then it gets put back on for whatever reason.

[#10]

@Lordwotsit 

Yes that is what I mean.  So it looks like it's not lack of SPF. although the lack of DKIM won't help, but shouldn't be causing the problem you see

@stuck you might have DKIM keys configured in your DNS but relay.plus.net won't know anything about a matching private key  and will not be DKIM signing your email..

However , as above that shouldn't be causing the problem UNLESS Hotmail etc have unilaterally decided that both SPF & DKIM are mandatoryor the lack of it is affecting the reputation of the PN servers ?

[#11]

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@MisterW wrote:

@stuck you might have DKIM keys configured in your DNS...

---

I don't think that comment was meant for me.  I don't have a domain name.  I'm a plain vanilla [myName]@[myAccountName.plus.com user.

[#12]

@stuck  thanks, correct it was meant for @SteveA  

My finger trouble

[#13]

@MisterW - yes I do, and the fact that I'm getting hotmail bounces points the issue away from FPS/DKIM and right back at MS blocking the IP addresses of the PN email servers.

[#14]

Still sees to be happening today

Simple mail  from XXX@yyy.plus.com to zzz@hotmail.co.uk using thunderbird client and relay.plus.net as the SMTP server

[#15]

Sill Broken

Final-recipient: rfc822; xxxxxxxx@hotmail.com
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=11BCD094B7733384] [CH2PEPF00000145.namprd02.prod.outlook.com 2026-02-11T18:48:56.558Z 08DE684A5D916225]

Last-attempt-Date: Wed, 11 Feb 2026 18:48:56 +0000