> On 3 Mar 2026, at 16:52, Jethro Binks via mailop <[email protected]> wrote:
>
> All,
>
> We were seeing these temporary deferrals for MS-related consumer domains from
> time to time in the last couple of weeks, after maybe a couple of days it
> would clear up and messages would be delivered onwards.
>
> However starting on 27th Feb we've got something different. Full hard
> rejections with: "550 5.7.515 Access denied, sending domain STRATH.AC.UK
> doesn't meet the required authentication level. The sender's domain in the
> 5322.From address doesn't meet the authentication requirements defined for
> the sender. To learn how to fix this see:
> https://go.microsoft.com/fwlink/p/?linkid=2319303 Spf= Pass , Dkim= Fail ,
> DMARC= Pass"
>
> For the particular server of ours that's involved in this (we've been sending
> from its IP for maybe 15 years), we are not doing any DKIM signing for
> Reasons. I had thought (rightly or wrongly) that either of SPF pass or DKIM
> pass was fine, that's certainly been the situation up to now. Something's
> changed somewhere though lately.
Lack of DKIM is likely the problem, they require all messages to be DKIM signed
<https://techcommunity.microsoft.com/blog/microsoftdefenderforoffice365blog/strengthening-email-ecosystem-outlook%E2%80%99s-new-requirements-for-high%E2%80%90volume-senders/4399730>
and have been rolling out enforcement since last year.
> Well, anyway, I thought I'd take one of the suggested routes in the forums
> and report athttps://olcsupport.office.com/.
>
> There's a big banner at the top: "We are aware of an issue that may result in
> certain IP addresses being temporarily rejected at higher rates. We are
> actively investigating the issue. Please continue to submit tickets if you
> are experiencing this problem.". Is that the temporary defer problem? Or
> the permanent reject one? Or some other problem? No idea, so I'll fill the
> form in anyway.
This message is related to a different issue connected to a different SMTP
response code.
> Except, I can't submit it. I get the error: "Website URL must start with
> http:// or https:// and contain a valid domain and top level domain.". I'd
> like to think I'd know my website address
> is "http://www.strath.ac.uk <http://www.strath.ac.uk/>", but apparently MS
> knows better and I'm wrong.
Maybe they are strictly enforcing the must be a TLD bit and excluding a lot of
working domains. But adding DKIM will make that bounce go away without having
to contact them.
Ken.
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