SMTP error 550 5.7.1 part of network is on block list

[#1]

I have received this bounceback on sending an e-mail from Outlook 365 on my PC using my Plusnet e-mail account to an Outlook.com recipient.

Part of the network on their blocked list?

Reporting-MTA: dns; euk22.eukhosting.net

Action: failed
Final-Recipient: rfc822;xx@yy.org.uk
Status: 5.0.0
Remote-MTA: dns; outlook-com.olc.protection.outlook.com
Diagnostic-Code: smtp; 550 5.7.1 Unfortunately, messages from [nnn.nnn.nnn.nn] 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=11BC29117274DD8A] [DS1PEPF0001709C.namprd05.prod.outlook.com 2025-10-29T11:01:47.997Z 08DE1488BC5141F0]

[#2]

Morning @ebforum 

Thanks for starting a new thread for the email error message. 

I've received the reply to my private message this morning and I will send the details to the relevant team for investigation. 

Thanks

Leanne.

[#3]

When they provide a remedy, can you please post back to here what it is, so that future occasions users are informed of the appropriate actions.

[#4]

Presumably this is a different issue from the severe blocklisting that was occurring for many weeks until about 2 weeks ago when it seemed to be resolved and Microsoft-owned addresses could be reached again. Has there been another outbreak of spam?

I note that, unless the sequence of n’s has been mis-typed, the blocked server is not a Plusnet avasout one, assuming their IP addresses haven’t changed (they were 212.159.14.nn and 84.93.230.nnn).

[#5]

Message to a single Hotmail address repeatedly fails as shown below.  Sent using Outlook from a xxxx@yyyyy.plus.com address.

Final-recipient: rfc822; xxxxxxxxxx@hotmail.co.uk
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 (S3150). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [Name=Protocol Filter Agent][AGT=PFA][MxId=11BC5D7679360942] [DB1PEPF000509E7.eurprd03.prod.outlook.com 2025-12-05T09:39:59.776Z 08DE2EBB4648F94A]

Last-attempt-Date: Fri, 05 Dec 2025 09:39:59 +0000

I assume these block lists are being investigated?

[#6]

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@Silver-Codger wrote:
...I assume these block lists are being investigated?

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You would hope so but this block by MS has been going on for sometime now so it seems that MS are not inclined to unblock the offending parts of the PN network.

Now if a Superuser ( @Townman @MisterW) or a member of Plusnet staff @plusnettony @dave) would give us mere mortals an update and correct the impression I give above, I'm happy to be told I'm completely misguided and it will be sorted very soon.