[AusNOG] Microsoft 365 - Junk Policy (last 2 weeks)

[Walker, Bill (Christchurch)]

Hi Luke/Dave,

Happening to 3 (out of 5) tenants I manage too, along with my personal mail that uses outlook.com

Thanks,

Bill

Bill Walker | Manager, Regional Networks | Stantec | Mobile: +64 21 241 7206

From: AusNOG <ausnog-bounces at lists.ausnog.net> On Behalf Of David Rawling
Sent: Friday, 31 March 2023 8:10 pm
To: ausnog at lists.ausnog.net
Subject: Re: [AusNOG] Microsoft 365 - Junk Policy (last 2 weeks)

Hi Luke

I can confirm that we've been seeing quite a lot of this across a number of Office 365 tenants; both our own and several we manage (I'll note that I am subscribed to AusNOG from my personal account not the affected tenant).

As we're one of the affected tenants, we've been able to dig quite deeply into the behaviour - in our case, it seems to be that almost all "new" messages in a thread are successfully delivered to us, but once it becomes a reply-fest it gets junked. There's some thought that it could be related to one or more links in our signature - not that it's a particularly large or "spammy" signature, though. No SPF, DMARC or DKIM failures here. No obvious reasons it would be marked junk - the SCL is below our threshold, etc.

What's frustrating is that so far, it's only affecting some people in our tenant. I've not had the problem with messages I send and receive, but there are others where it's 90% failure. I do have a different signature file - very different formatting though it looks the same to the recipient. I was thinking that might be related, but no dice so far.

So you're not alone but we have absolutely no idea what's breaking.

Dave.

--
David Rawling - Principal Consultant
PD Consulting and Security

t: +61 41 213 5513  |  e: djr at pdconsec.net<mailto:djr at pdconsec.net>

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On Fri, 2023-03-31 at 16:55 +1100, Luke Thompson wrote:
Hi all,

Strange question though curious if anyone's seen the same.

We've had a range of clients reporting very intense junking behaviour
with M365, whether sending or receiving, if there's a M365 tenant
involved it seems to be hitting Junk for reasons that aren't clear. This
is with SPF/DKIM/DMARC/etc all passing.

I'm wondering if potentially a new policy has shipped which is
over-reaching somewhat, as no bounce-backs are being received so it's a
case of delivered-but-not. This is across a range of clients and
clients' clients.

If we'd only heard of this from a single client we'd not think much of
it, though this is both ways and across a range of tenants. Would be
good to know if there's any substance to it.

As we don't run M365 nor have responsibility for impacted tenants, the
request here is to check with the IT community. Thank you.

Cheers,
Luke

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