From address doesn't meet the authentication requirements defined for the sender
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Re: From address doesn't meet the authentication requirements defined for the sender
20-10-2025 10:45 AM - edited 20-10-2025 10:47 AM
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Disappointed that the word of super users who have deep understanding of the technology and good working relationships with the business is not good enough for you. If you reflect back through this long thread you might realise that the messages given throughout by all of the super users are consistent with the final resolution.
Subsequent to the addition of SPF on all subdomains this became a Microsoft fault requiring a remedy from Microsoft.
It should though be noted, that this is probably not a systemic fix - other providers might well still encounter the same issue.
In another browser tab, login into the Plusnet user portal BEFORE clicking the fault & ticket links
Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.
If this post helped, please click the Thumbs Up and if it fixed your issue, please click the This fixed my problem green button below.
Re: From address doesn't meet the authentication requirements defined for the sender
20-10-2025 11:06 AM
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@Townman It's not that the word of Superusers is not good enough. I have a deep respect for the work you have done in keeping this long running, and at times wide ranging, topic on track. Especially as it has been you and your fellow Superusers that have had to deal with the brunt of the anger and frustration from customers. I know that what you all have been saying from very early on is consistent with where we are now.
My point is one that has been made many times throughout this topic. It is not hard and it would be courteous and it would do wonders for customer relations for an actual member of Plusnet staff to communicate this (good) news with their customers.
All they (@plusnettony??) need to do is confirm that, to the best of their knowledge, the root cause of this problem, which we all know was not something Plusnet or any of the other impacted mail providers, could correct, has been addressed and thus this problem is fixed - at least until the next time the goalposts are moved.
There's even a sticky post where they could make such an announcement :https://community.plus.net/t5/Email/Microsoft-email-issue/td-p/2017289. Or the original topic by @James_B: https://community.plus.net/t5/Service-Information/Sending-emails-to-Microsoft-owned-domains-such-as-...
Re: From address doesn't meet the authentication requirements defined for the sender
20-10-2025 3:08 PM
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It's good to feel that the DKIM issue might finally have been resolved so my thanks to anyone in Plusnet who helped persuade Microsoft to make the change.
Can you confirm whether any avasout servers remain on block lists (e.g. see #681) or has that matter also been dealt with?
Re: From address doesn't meet the authentication requirements defined for the sender
23-10-2025 8:43 PM
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Posts unconnected with this topic merged with duplicate thread
Re: From address doesn't meet the authentication requirements defined for the sender
26-10-2025 12:09 PM
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Post unconnected to this subject matter moved to its own topic and re-titled.
Re: From address doesn't meet the authentication requirements defined for the sender
29-10-2025 1:13 PM - edited 29-10-2025 1:14 PM
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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]
Re: From address doesn't meet the authentication requirements defined for the sender
29-10-2025 4:02 PM
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@ebforum The error you report is not the problem discussed in this topic.
@Baldrick1 should be able to move your post to the correct topic, which I think is this one:
Re: From address doesn't meet the authentication requirements defined for the sender
29-10-2025 4:13 PM - edited 29-10-2025 4:20 PM
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This and that are NOT the same issue.
The referred to thread is about individual users being black listed and is encountered on the attempt to SEND
This issue is about Plusnet’s servers being black listed and is accounted on the attempt to DELIVER. They need different remedies.
By all means there is merit in splitting this to an appropriate focus, but not one which confuses an established thread. The existing thread needs cyber security involvement. This I suspect is a matter for net ops.
A suitable title might be "SMTP error 550 5.7.1 part of network is on block list"
Might the relevant posts and responses be moved and sanitised please?
In another browser tab, login into the Plusnet user portal BEFORE clicking the fault & ticket links
Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.
If this post helped, please click the Thumbs Up and if it fixed your issue, please click the This fixed my problem green button below.
Re: From address doesn't meet the authentication requirements defined for the sender
29-10-2025 4:15 PM
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Hi there @ebforum
Thanks for letting us know.
To help you with this error message, I've sent you a private message to get some extra details.
Speak to you soon ![]()
Leanne.
Re: From address doesn't meet the authentication requirements defined for the sender
29-10-2025 5:15 PM
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As per @Townman I have set up a new thread with the title suggested by him:
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