---
title: "Cold Email Deliverability News and Inbox Rules Index"
description: "What changed in Gmail, Outlook and Yahoo sender rules, plus the Inbox Rules Index: a DNS measurement of how many business domains enforce DMARC."
url: "https://www.emailchaser.com/deliverability-news"
content_type: "text/markdown"
---

Deliverability briefing, Saturday, 5 September 2026

# aon.com and zoho.com tighten mail-spoofing settings

No cold email story cleared our bar for corroboration today, so the movers in our panel are the news. aon.com and zoho.com both tightened the settings that let mail servers reject messages forged in their name. Across the 499 companies we track, the overall picture held steady from yesterday.

## Inbox Rules Index

499 of 499 companies checked, Saturday, 5 September 2026

On each measurement we look up the published email settings of the same 499 real companies, the kind you send cold email to. This is what they have set up, not a score on your own sending.

88.4%no change

block forged mailthey tell mail servers to junk or bounce anything faking their addressDMARC at quarantine or reject

70.3%

at the strictest settingbounce it outright rather than putting it in spamDMARC p=reject

43.1%

keep a locked sender listmail sent from anywhere off that list fails the checkSPF -all

6.4%

ask for encryptionsome of these refuse mail unless your server has a valid security certificateMTA-STS record published

Today's panel shows 88.4% of the 499 companies we track block mail that fakes their address, unchanged from yesterday and up 0.6 percentage points from our 10 August baseline. That figure describes how these companies protect their own name, not how your cold email is judged when it lands in their inbox.

### What this means for your sending

Proofpoint screens more of these companies than anything else, at 33.9%, so it is the filter most of your cold email actually meets. 6.4% ask senders for an encrypted connection, so an expired or mismatched certificate on your sending server can stop mail reaching them at all. 2.4% cannot receive email at all, which is dead weight on any list that includes them. The rest is about how these companies stop others forging their address. It is a good sign of how seriously they run email security, but it is not what decides where your mail lands: that is judged against your own domain's records.

### Who changed their setup

<table class="jss55"><tbody><tr><td class="jss56 jss57">aon.com</td><td class="jss56">Sender list: loose list → <strong>locked list</strong></td><td class="jss56" style="text-align:right"><span class="jss58" style="background:#E8F5ED;color:#1B7F4C">stricter</span></td></tr><tr><td class="jss56 jss57">zoho.com</td><td class="jss56">Sender list: nothing published → <strong>locked list</strong></td><td class="jss56" style="text-align:right"><span class="jss58" style="background:#E8F5ED;color:#1B7F4C">stricter</span></td></tr></tbody></table>

2 of these companies changed their email setup since Friday, 4 September 2026: 2 got stricter. If any are on your list, the stricter ones are running their email security actively.

### Whose spam filter your email meets

<table class="jss49"><tbody><tr><td class="jss50">Proofpoint</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:33.9%;background:var(--ec-accent)"></span></span></td><td class="jss52">33.9%</td></tr><tr><td class="jss50">Microsoft 365</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:26.1%;background:var(--ec-accent)"></span></span></td><td class="jss52">26.1%</td></tr><tr><td class="jss50">Google Workspace</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:18.8%;background:var(--ec-accent)"></span></span></td><td class="jss52">18.8%</td></tr><tr><td class="jss50">Their own servers, or unknown</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:9.6%;background:var(--ec-accent)"></span></span></td><td class="jss52">9.6%</td></tr><tr><td class="jss50">Mimecast</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:4%;background:var(--ec-accent)"></span></span></td><td class="jss52">4%</td></tr><tr><td class="jss50">Cisco Secure Email</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:3.8%;background:var(--ec-accent)"></span></span></td><td class="jss52">3.8%</td></tr></tbody></table>

Proofpoint screens about one in every 3 of these companies, more than any other filter. This is the software that reads your email before a person does. It says nothing about how any one of them treats your mail.

### Which industries guard their name hardest (companies checked)

<table class="jss49"><tbody><tr><td class="jss50">Software (126)</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:97.6%;background:var(--ec-accent-ink)"></span></span></td><td class="jss52">97.6%</td></tr><tr><td class="jss50">Finance (54)</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:94.4%;background:var(--ec-accent-ink)"></span></span></td><td class="jss52">94.4%</td></tr><tr><td class="jss50">Services (28)</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:92.9%;background:var(--ec-accent-ink)"></span></span></td><td class="jss52">92.9%</td></tr><tr><td class="jss50">Healthcare (47)</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:89.4%;background:var(--ec-accent)"></span></span></td><td class="jss52">89.4%</td></tr><tr><td class="jss50">Logistics (17)</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:88.2%;background:var(--ec-accent)"></span></span></td><td class="jss52">88.2%</td></tr><tr><td class="jss50">Retail (50)</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:88%;background:var(--ec-accent)"></span></span></td><td class="jss52">88%</td></tr><tr><td class="jss50">Travel (25)</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:88%;background:var(--ec-accent)"></span></span></td><td class="jss52">88%</td></tr><tr><td class="jss50">Energy (24)</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:87.5%;background:var(--ec-accent)"></span></span></td><td class="jss52">87.5%</td></tr><tr><td class="jss50">Media (26)</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:84.6%;background:var(--ec-accent)"></span></span></td><td class="jss52">84.6%</td></tr><tr><td class="jss50">Telecoms (30)</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:80%;background:var(--ec-accent)"></span></span></td><td class="jss52">80%</td></tr><tr><td class="jss50">Industrial (44)</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:79.5%;background:var(--ec-accent)"></span></span></td><td class="jss52">79.5%</td></tr><tr><td class="jss50">Schools and universities (28)</td><td class="jss51"><span class="jss47"><span class="jss48" style="width:57.1%;background:var(--ec-ink-300)"></span></span></td><td class="jss52">57.1%</td></tr></tbody></table>

Software guards its name hardest: 97.6% block mail faking their address. Schools and universities least, at 57.1%, a gap of 40.5 points. A high number means that industry runs email security tightly, so expect your own setup to be looked at more closely there.

499 of the 499 companies we check answered on this measurement. The same fixed panel of real companies, measured over public DNS on each run. This is what the people you email have set up, not a score on your own sending.

No deliverability news today was confirmed by two separate publications, so there is none here. The numbers below are still today's.

## What these numbers mean

### Does 88.4% enforcement mean my cold email gets rejected?

No. That 88.4% measures whether a company blocks mail forged as them, not how they treat mail arriving from you. Your delivery depends on your own domain's settings, not theirs.

### Which gateways sit in front of the companies you email?

Proofpoint sits in front of 33.9% of the companies in our panel, Microsoft 365 in front of 26.1%, and Google Workspace in front of 18.8%. These are the gateways that scan your mail first, before it ever reaches an inbox.

### What actually changed today?

aon.com and zoho.com both moved their SPF setting, the rule that lists which servers may send as their domain, from a loose setting to a strict one. Nothing else in the 499-company panel shifted, and the overall enforcement rate stayed at 88.4%.

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## Check your own sending

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[← Friday, 4 September 2026](https://www.emailchaser.com/deliverability-news/2026-09-04)[All briefings](https://www.emailchaser.com/deliverability-news)

## Every briefing

2026-09-05[aon.com and zoho.com tighten mail-spoofing settings](https://www.emailchaser.com/deliverability-news/2026-09-05)index only · DMARC 88.4%

2026-09-04[Exchange servers face more throttling and blocking](https://www.emailchaser.com/deliverability-news/2026-09-04)2 stories · DMARC 88.4%

2026-09-03[Microsoft update breaks Outlook and Teams on Arm PCs](https://www.emailchaser.com/deliverability-news/2026-09-03)2 stories · DMARC 88.4%

2026-09-02[Proofpoint is the gateway most likely to scan your email](https://www.emailchaser.com/deliverability-news/2026-09-02)index only · DMARC 88.4%

2026-09-01[Microsoft 365 outage causes auth failures for hours](https://www.emailchaser.com/deliverability-news/2026-09-01)1 stories · DMARC 88.4%

2026-08-31[thermofisher.com switches mail filter to Proofpoint, Zoho tightens SPF setting](https://www.emailchaser.com/deliverability-news/2026-08-31)index only · DMARC 88.4%

2026-08-28[Most Of The Companies You Email Sit Behind Proofpoint Or Microsoft](https://www.emailchaser.com/deliverability-news/2026-08-28)index only · DMARC 88.4%

2026-08-26[DMARC enforcement holds at 88.4% with no new deliverability story](https://www.emailchaser.com/deliverability-news/2026-08-26)index only · DMARC 88.4%

2026-08-15[No deliverability stories today: DMARC enforcement climbs to 88.1%](https://www.emailchaser.com/deliverability-news/2026-08-15)index only · DMARC 88.1%

2026-08-10[A Klaviyo sign-up bug may have shown saved passwords to advertisers](https://www.emailchaser.com/deliverability-news/2026-08-10)1 stories · DMARC 88%