Diagnostic-Code: smtp; 550 5.7.1... ...part of their network is on our block list (S3150)

[#1]

Is anyone still seeing this error?

Diagnostic-Code: smtp; 550 5.7.1 Unfortunately, messages from [x.x.x.x] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150).

Looking at our logs I can't see any since 14:22 yesterday so hoping this is working.

[#2]

@dave Yes, me.

The outgoing message was sent at 11:06 today Mon 8 Dec 2025.

The bounce came back at 14:51.

The outgoing message was sent to a Hotmail address from one of my secondary mailboxes

The bounce details are:

Final-recipient: rfc822; [theCorrectNameHere]@hotmail.com
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=11BC5D34B88F8B25] [AM2PEPF0001C715.eurprd05.prod.outlook.com 2025-12-08T14:50:53.126Z 08DE2E9A697BEB74]

Last-attempt-Date: Mon, 08 Dec 2025 14:50:53 +0000

[#3]

Would you be able to PM me the from address please? I'll see what we can see.

[#4]

---

@dave wrote:

Would you be able to PM me the from address please?

---

Just done that.

Thank you for looking into this.

[#5]

Arrival-Date: Mon, 08 Dec 2025 11:18:00 +0000


Final-recipient: rfc822; [[emailaddress]]s@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=11BC6859CAF4FEA8] [AM4PEPF00027A64.eurprd04.prod.outlook.com 2025-12-08T15:02:19.728Z 08DE342CE85E2B73]

Last-attempt-Date: Mon, 08 Dec 2025 15:02:19 +0000

[#6]

@dave ,   Yes, another one here sent to a Hotmail address at 14:23 today

Reporting-MTA: dns; avasout-peh-001 [212.159.14.17]
Received-From-MTA: dns; yyyyyy[nnn.nnn..nn.nnn]
Arrival-Date: Mon, 08 Dec 2025 14:23:29 +0000

Final-recipient: rfc822; xxxxxx@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=11BC5CE53D983665] [DU6PEPF0000B620.eurprd02.prod.outlook.com 2025-12-08T14:26:29.146Z 08DE2E72AC6AE0E8]

Last-attempt-Date: Mon, 08 Dec 2025 14:26:29 +0000

[#7]

@dave Please can we have an update on this problem?

Things do seem to have changed for me but it's still not right.

This morning I sent a test message From the secondary mailbox I gave you details of in a PM To an outlook.com address.

That test message was delivered, which is an improvement as it didn't bounce but it was delivered to the Junk folder, not the Inbox, which can be worked around but is far from ideal.

[#8]

@Silver-Codger thanks, I can see a batch of the same error on Monday afternoon evening but not seeing any since 18:27 on Monday with that specific error so that looks to have cleared up for now.

@stuck I can see a message from you to an Outlook address at 11:12am today so guessing that's the one. On our side it shows delivered OK, no grey listing or other indication from Microsoft they had a problem with it, whole process took 4 seconds so they've not backed anything off.

Let me do some testing on mine and see where that ends up.

[#9]

@dave Thank you for the update.

Yes the test message I sent today was sent at that time, and yes, it reached the outlook.com address very quickly, so yes it wasn't grey listed but there must have been something odd about it because it ended up in the Junk folder.  That it went there and not to the Inbox is irritating but I should be able to work around it by whitelisting the sending Plusnet address.

At least the block seems to have been lifted.

[#10]

@dave Thanks for the update and sorting it out.

I sent a message to the same Hotmail adress at 23:47 on Monday evening and it seems to have worked OK. (No proof of delivery but I have not recceived any message delivery failure report)..

I hope things continue to stay stable.