Rejection of some outgoing emails + attachments since July 2025

[#1]

I’ve been sending emails and occasional attachments via Microsoft Outlook (previously Windows Live Mail) and my internet provider Plusnet for over 14 years without any problems whatsoever ~ until 22^nd June 2025 when emails plus attachments to the following accounts began bouncing back or disappearing, as follows: ~

• An email plus a few photo JPEGS to my elder daughter (on Hotmail) was bounced back on the grounds Code: smtp; 550 5.7.515 Access denied ~ but when copied to her husband (Yahoo.co.uk) the email plus photos was accepted
• The same email plus photos was sent to my younger daughter (Gmail.com) and granddaughter (icloud.com). The email to my younger daughter simply disappeared and cannot be found ~ not in the spam folder. On the other hand, my granddaughter received the email & photos!
• Just to add further confusion for this 82-year-old ~ the same old photos sent to a friend who like my younger daughter ~ also uses Gmail ~  were received by him!

I should add that although the above problem continues where attachments or computer links are involved, simple emails to my daughters are being received by them

I have not undertaken any changes to my computer nor added any new antivirus programmes though Microsoft Office continues to update periodically.

To summarise, since late June 2025 my emails plus attachments have been rejected by Hotmail, have apparently disappeared per one Gmail user but have been received another Gmail user---- and also accepted, as normal, by users of Yahoo & iCloud!

What is going on?

If this newly emerged problem is at my end then is the issue with my Plusnet account, Outlook or Microsoft?  If so, then Is it one which I can resolve and how?

Thanks for your help.

[#2 · Accepted solution]

Its all detailed here https://community.plus.net/t5/Email/From-address-doesn-t-meet-the-authentication-requirements/m-p/20...

[#3]

Many thanks for the prompt response.

Having ploughed through four weeks of correspondence , I can see that the issue is far outside my ability to resolve.

At least my basic emails are, for the time being,  still getting through to the various Hotmail, Gmail and other accounts listed . It is only when I attach photos or internet links that they are rejected or disappear.

[#4]

@CSG 

When you attach files and / or add links, you raise the the SPAM risk level which given the draconian measures undertaken by Microsoft recently probably now has a higher threshold than it did.  Therefore is take very little now to trigger the alarms.

Gmail is playing really silly beggars right now deferring delivery of emails, sometimes for as long as / longer than 5 days.  It is not until the sending service gives you the valiant attempts to deliver will an NDR be returned.  I have now got a soup to nuts example with the support gurus - send 7th July, NDR received on the 11th.

There has been a merry dance attempting to sort out the Microsoft space, which appears to be largely resolved ... except when addressing several Microsoft accounts on the same email - then internal performance issues within Microsoft appear to give rise to incorrect levels of suspicion ... apparently known about for a good while, which Microsoft are either incapable of fixing, or disinclined to fix.

Are you sending from you@youraccount.plus.com or from you@yourdomain.co.uk hosted by Plusnet?  Although sent through the same email services, they have different anti-spam measures.

[#5]

Yes, I can see that attachments or computer links have been adding to the failure rate of my recent outgoing emails.

For the time being I simply copy emails to other members within each household whose email addresses still accept my emails ----- Yahoo and iCloud.

it is however puzzling that whilst all emails to my younger daughter with Gmail are "disappearing", those with several photos to a very, very old friend on Gmail continue to be accepted.

I have been with Plusnet since 2010 and I am sending emails from me@my account.plus.com.  I see that the email service has/is being   sold off and guess that, reluctantly, I may have to consider moving if things don't improve.

Thanks again.

[#6]

These current issues probably do not have anything to do with the Plusnet email service or it being out sourced on behalf of Plusnet to a third party.

Both Microsoft and Gmail have recently moved various goal posts to the other side of the football pitch and I do not mean the ends, but literally to the sides!  Without trying to blind you with science...

• All *.plus.com email users are now being treated by these email services as one single bulk email user and thus now have draconian bulk sender polices applied - to any sensible thinking person we are each individuals so this is utter madness / nonsense from the outset
• Consequently the following are required (do not worry what they are)...
  1. SPF configuration
  2. DKIM configuration
  3. DMARC configuration

Previously (1) or (2) and (3) were adequate as individual email senders; Plusnet has implemented (2) and (3) on users accounts for several years and all was well.  Treating all Plusnet users as a single user now requires that ALL THREE are present and pass testing.

Plusnet has therefore added (1) to the configuration.

At the other end of things, there are reports (observations that in the verification of 2) that Microsoft's servers are not robust enough to process all of the additional verification work they have placed on themselves so that there are elevated levels of false negatives (failures) of validation.  That is leading o delivery failures.

As for Gmail, something different is happening ... they are repeatedly deferring acceptance of sent emails.  Sending services will keep attempting to deliver for 5 days, after which a NDR should be received.

The observation of your very old friend on Gmail not experiencing an issue - is there's a free Gmail account or a subscription based email account?  Gmail has traditionally not placed unhelpful burdens on accounts which people are paying for.  Similarly Googlemail addresses have similarly been free from unhelpful practices.

[#7]

Thanks for the  helpful sit rep, Townman.

1) 

Previously (1) or (2) and (3) were adequate as individual email senders; Plusnet has implemented (2) and (3) on users accounts for several years and all was well.  Treating all Plusnet users as a single user now requires that ALL THREE are present and pass testing. Plusnet has therefore added (1) to the configuration.

When was (1) added to the configuration? When would one expect this to take effect? Doesn't seem to have helped with emails to Gmail addresses so far.

2) As for Gmail, something different is happening ... they are repeatedly deferring acceptance of sent emails.  Sending services will keep attempting to deliver for 5 days, after which a NDR should be received.

For the record, I've had many emails to Gmail recipients go missing for much longer than five days but I've only ever had one NDR.

[#8]

The addition of SPF is what fixed the Microsoft issue.

Has that caused disquiet for Gmail?  It being time coincident might be just that, a coincidence.

From the diagnostic information I have seen, there is little useful information in the 30+ delivery acceptance deferrals recorded from Gmail.  Some reading I have done (way above my understanding) could be read as to suggest that Gmail wants the same methods as Microsoft ... but implemented differently, but that is because their "imposed rules" are not written unambiguously.  The inspection continues ... 

The NDR notification does seem potentially inconsistent ... as does delivery to Gmail.  From a different Plusnet email address, early Tuesday morning I sent an email from a test account.plus.com to my Gmail account.  It was delivered in 181 seconds.

I sent another from the same account a few minutes later ... I am still awaiting some indication of what / where.  I expect a NDR on July 20th.

I am wondering if email services process NDRs similar to OOO messages - for a given time frame for a given recipient, a given sender is sent only one email notification.  I'll ask the question.