topic Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting in Email

Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

hem2026 — Wed, 25 Feb 2026 18:36:18 GMT

I am sending email via Plusnet’s SMTP servers. The sending IP shown in the
Microsoft bounce is 212.159.14.17, which resolves to avasout03.plus.net and
belongs to Plusnet Plc (AS6871). Microsoft has blocklisted this IP with error
S3140. Because this is a Plusnet-owned outbound mail server, only Plusnet can
request delisting via Microsoft SNDS/JMRP. Please escalate this to the email
platform team for investigation and delisting.

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

stuck — Wed, 25 Feb 2026 19:06:18 GMT

This problem has being going on for weeks. The main (but not the only) topic about is this one:

https://community.plus.net/t5/Email/Hotmail-rejecting-mail-from-PN-Diagnostic-Code-smtp-550-5-7-1/td-p/2035800

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

hem2026 — Thu, 26 Feb 2026 09:11:11 GMT

Thanks. I have raised a complaint/question with Plusnet.

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

plusnettony — Fri, 27 Feb 2026 10:18:36 GMT

We're really sorry this is an ongoing issue, I can assure you it's been raised with Microsoft.

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

abitpedantic — Fri, 27 Feb 2026 10:58:30 GMT

@plusnettony @MisterW

A couple of days ago, on another thread, I wrote:

"I gather that even after migration to Greenby, outgoing email is going via Plusnet’s servers for the foreseeable future. Is this because Greenby don’t have servers available or they are declining to deploy them for fear of them immediately becoming blocklisted due to the ongoing problems that, for once, are not of their making?".

At least, that's how it appears to me. Would either of you be able to provide definitive statements on the points raised?

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

plusnettony — Fri, 27 Feb 2026 11:23:04 GMT

Outbound email will move to Greenby at a later date. The timing is our decision, but there are a few complexities on our side that we need to work through first to avoid causing issues for some users. We’ll share more updates as soon as we’re ready to make the switch.

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

Protech — Fri, 27 Feb 2026 11:49:58 GMT

@plusnettony

Can you confirm that this represents the current pre and post migration status as currently planned

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

plusnettony — Fri, 27 Feb 2026 12:07:29 GMT

Essentially, yes.

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

mavison — Fri, 27 Feb 2026 14:40:39 GMT

@plusnettony wrote

Outbound email will move to Greenby at a later date.

Does this apply to all brands?

I seem to remember reading somwhere that Force9 had already moved output to Greenby?

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

plusnettony — Fri, 27 Feb 2026 14:45:42 GMT

Some have been done, some not. The answer above specifically refers to relay.plus.net.

Eventually, all will be migrated to Greenby.

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

hem2026 — Fri, 27 Mar 2026 16:04:07 GMT

Received this via email today:

Thank you for your ongoing patience.

Whilst it's not yet fully resolved, improvement has been made and outbound emails to Microsoft addresses do appear to now be working to greater extent. We continue to work with Microsoft for a full resolution.

Should you continue to experience the problem from today (27/03) please receive examples of the email headers related to the issue.

Should I not hear back by 02/04 I will work on the basis that the matter is resolved for you.

Kind regards,

Matt Sladden

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

redsox9 — Sat, 28 Mar 2026 07:56:09 GMT

Got through to msn.com contacts last night for the first time in months. Let's hope the Microsoft door stays open permanently to Plusnet/Greenby servers.

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

hem2026 — Sun, 05 Apr 2026 07:39:41 GMT

So much for that. My emails to hotmail addresses are being rejected again. Plusnet's closing response to my complaint said that my service had been moved to Greenby, but I've not had any notification from Greenby. Have complained again to Plusnet.

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

pvmb — Sun, 05 Apr 2026 09:53:58 GMT

...But are your emails being sent by a Greenby host, or via existing Plusnet hosts - for now? I don't know.

So, what's occurring?

Well here is one I successfully sent earlier (to myself @ BT Email) via the Greenby Webmail service:
(IP address 213.5.176.224 is Greenby - https://www.whois.com/whois/213.5.176.224)

Authentication-Results: btinternet.com;
dmarc=pass header.from=<PN Username>.plus.com;
dkim=none;
spf=none smtp.helo=demian.gateway.enmail.co;
spf=pass smtp.mailfrom=<PN Username>.plus.com;
arc=none smtp.remote-ip=213.5.176.224
X-OWM-SPF-MAILFROM: Pass
X-OWM-SPF: 0

Received-SPF: none (btprdrgi040.btinternet.com: domain
demian.gateway.enmail.co does not designate permitted sender hosts)
identity=helo; receiver=btprdrgi040.btinternet.com; client-ip=213.5.176.224;
helo=demian.gateway.enmail.co;
Received-SPF: pass (btprdrgi040.btinternet.com: domain <PN Username>.plus.com
designates 213.5.176.224 as permitted sender) identity=mailfrom;
receiver=btprdrgi040.btinternet.com; client-ip=213.5.176.224;
envelope-from=<PN Email>@<PN Username>.plus.com; helo=demian.gateway.enmail.co;

X-Originating-IP: [213.5.176.224]
X-OWM-Source-IP: 213.5.176.224
X-OWM-Env-Sender: <PN Email>@<PN Username>.plus.com
X-SNCR-Rigid: 697AF6A81BCB7E76
X-OWM-DMARC-DOM: plus.com
X-OWM-DMARC: spf 0 dkim 7
X-OWM-DKIM: 5
X-VadeSecure-score: verdict=clean score=0/320, class=clean
X-SNCR-VADESECURE: CLEAN
X-RazorGate-Vade: Zzzzz.............................................!
X-RazorGate-Vade-Verdict: clean 0
X-RazorGate-Vade-Classification: clean

Received: from demian.gateway.enmail.co (213.5.176.224) by btprdrgi040.btinternet.com
id 697AF6A81BCB7E76 for ******@******.com; Sun, 5 Apr 2026 09:52:12 +0100
Received: from mail.enmail.co (unknown [91.204.208.8])
by gateway1.enmail.co (Postfix) with ESMTPS id EBF3D41B46
for <******@******.com>; Sun, 5 Apr 2026 08:52:11 +0000 (UTC)
Received: from mail.enmail.co (localhost [127.0.0.1])
by mail.enmail.co (Postfix) with ESMTP id BA3E1C0788
for <******@******.com>; Sun, 5 Apr 2026 08:52:11 +0000 (UTC)
Received: from webmail.greenby.com (192-168-116-62.hostns-roundcube.enmail-prod.svc.cluster.local 
[192.168.116.62])
by mail.enmail.co (Postfix) with ESMTPA id 8E070C06E5
for <******@******.com>; Sun, 5 Apr 2026 08:52:11 +0000 (UTC)
MIME-Version: 1.0
Date: Sun, 05 Apr 2026 09:52:11 +0100
From: "******" <PN Email@PN Username.plus.com>
To: ******@******.com
Subject: Route Test -

BTW, IP address 212.159.14.17 is a Plusnet host: Whois IP 212.159.14.17

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

abitpedantic — Sun, 05 Apr 2026 10:06:10 GMT

My understanding is that if you use Greenby webmail, your outgoing messages will go through their servers i.e. mail.enmail.co whereas if you are using a client (e.g. MS Outlook), your outgoing messages are routed according to what you set up in the client. The expectation (i.e. official recommendation) is that relay.plus.net (which translates to 212.159.14.17 amongst others) is used but there's nothing to stop you specifying mail.enmail.co instead.

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

pvmb — Sun, 05 Apr 2026 10:24:05 GMT

...I suspected something like that but, as I am not using client email programs, I am not up on what all the correct settings, and credentials, need to be. I get the impression from posts around here many users of said programs don't know - or understand - either! Consequently they are taking the simple approach: Blame it all on Greenby.

I, and presumably others, know that the Greenby email system does work. That doesn't mean there have not been some bumps and glitches along the way - it wasn't all as completely seamless as Plusnet suggested it would be but, for straightforward, simple Plusnet email users it was simple enough. Might be genuine complications for people with other, or more complicated, email setups.

It's also possible that coincidence has come into play - many have been complaining of increasing Spam before the transfer to Greenby, plus users of other ISPs (e.g. Zen) have also recently been having issues with getting emails through to certain destinations. I reckon these are likely Spam related problems.

But then, I've also seen people on this BB bitterly complaining about getting Spam to their QUOTED email address... They get Spam?! Whatever next? Will they be accusing The Pope of being a Catholic? 🤣

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

jab1 — Sun, 05 Apr 2026 10:32:04 GMT

@pvmb wrote:

It's also possible that coincidence has come into play - many have been complaining of increasing Spam before the transfer to Greenby, plus users of other ISPs (e.g. Zen) have also recently been having issues with getting emails through to certain destinations. I reckon these are likely Spam related problems.

Although I don't use the Zen email facility - got caught in their decision to end it for 'new' users - I am not aware of complaints.

I use a client program for mail, my setup is not exactly 'standard', but apart from a reluctance to start cleanly, I have no issues with my migrated service.

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

pvmb — Sun, 05 Apr 2026 10:48:53 GMT

Microsoft Domain Blacklist Causes Email Problems for UK ISP Zen Internet
Thursday, Mar 19th, 2026

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

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

redsox9 — Sun, 05 Apr 2026 11:33:23 GMT

@abitpedantic wrote: The expectation (i.e. official recommendation) is that relay.plus.net (which translates to 212.159.14.17 amongst others) is used but there's nothing to stop you specifying mail.enmail.co instead.

Which one will get us through the blacklists of iCloud, me.com, msn.com, hotmail etc., avoiding spam in the process?

Re: Plusnet SMTP IP 212.159.14.17 blocklisted by Microsoft (S3140) – needs delisting

abitpedantic — Sun, 05 Apr 2026 15:32:08 GMT

It needs someone who uses both methods to say what works. I only use mail.enmail.co and recently:

a) I've had no trouble reaching hotmail and other MS-owned addresses

b) All my attempts to reach gmail addresses were being bounced but this morning a couple of emails were delivered instantly

c) No joy for ages with icloud (Diagnostic-Code: smtp; 554 5.7.1 [BS01] Message rejected due to local policy)

Of course, everything is so ridiculously unpredictable that tomorrow I could be writing a completely different list.