# Non-Human Interactions (NHI) and Email Metrics

> M3AAWG's Nov 2020 study of automated "bot clicks" from security scanners — <10% B2C vs 20–80% B2B click/open inflation, why filtering NHI out is unreliable, and the practices that reduce it.

Source: emailmarketing.net — https://emailmarketing.net/learn/operations/non-human-interactions

If your click or open rates look higher than real engagement could explain, software may be clicking your links and opening your messages before your recipients do. These non-human interactions (NHI) can inflate business-to-business (B2B) metrics by a large margin, and they cannot be filtered out reliably.

The figures below come from a study by the Messaging, Malware and Mobile Anti-Abuse Working Group (M3AAWG): *M3AAWG Exploring the Impact of Nonhuman Interactions on Email Send Metrics*, November 2020 (M3AAWG-136). The document gives its own address as m3aawg.org/sites/default/files/nhi.pdf. The original queue URL on m3aawg.org now returns a 404 error, so the document was retrieved through the Wayback Machine (snapshot 2025-12-11).

NHI, also called "automated clicks", is the automated handling of received email by software rather than by the recipient. It typically happens during **security scans by a mailbox provider's antivirus and security software**. The system follows the links in an email and visits the target site to analyze its content (looking for malware and phishing pages). Along the way it registers a "click" or an "open" for the campaign and pollutes website analytics.

The scanning patterns are deliberately hard to recognize, so that bad actors cannot get around the scanning. Symptoms range from clicks on some of the links to **every link in every email to a domain being clicked in quick succession**.

What began as a statistical anomaly has become "a major issue affecting email campaign metrics in a massive way". Senders who relied on open and click rates to measure performance may need additional measures of success. NHI on clicks is closely related to the way Apple Mail Privacy Protection (MPP) and Gmail's image prefetching inflate opens (see [Metrics & Benchmarks](https://emailmarketing.net/learn/operations/metrics-and-benchmarks)).

## Measured impact (M3AAWG benchmark study)

Method: the study used benchmark data from large and small ESPs and from B2B and business-to-consumer (B2C) senders across the industry, in some cases covering several years of send, click and open data. It set out to test whether browser **user-agent strings could reliably identify NHI**, and whether NHI could be reliably filtered out to recover a true click rate.

| Segment | NHI impact on metrics | Notes |
|---|---|---|
| **B2C** | Generally **< 10%** | Large volumes go to a smaller set of large consumer inbox providers. The figure was consistent throughout the research. **The impact is weaker for more reputable brands** |
| **B2B** | **20–80%** | Enterprise anti-spam software is stricter on inbound mail. The range correlated with recipient engagement: **the lower the engagement at an inbox provider, the higher the probability of NHI scans** |

The study could not break NHI levels down by vertical market segment in a meaningful way. An overall effect across the industry is hard to quantify, because **filter vendors and internet service providers (ISPs) actively hide their scanning from detection**, which they must do so that filters are not circumvented. Any filtering effort therefore leaves a margin of error in "NHI-adjusted" rates.

The study did find a strong **correlation between reputation and NHI**. M3AAWG recommends building and maintaining a positive reputation to reduce the impact of NHI on open and click rates.

## Business impact

- **E-commerce**: automated clicks and opens can **trigger marketing automations and follow-up emails**. Unreliable metrics make planning for return on investment (ROI) and return on ad spend less accurate. The cost is more in lost opportunities than in lost revenue.
- **Media and content marketing**: clicks and site visits are often the conversion metric itself. Strategies based on guaranteed clicks, opens or article views can no longer rely on those numbers. This directly reduces advertising and subscription revenue, and threatens marketing revenue that depends on lead generation. M3AAWG advises strengthening **form and email verification** to keep list quality high.
- **Brand and ESP reputation**: as engagement indicators become less reliable, it gets harder to segment by engagement and to sunset recipients. List quality then declines, and real engagement falls, which lowers domain reputation. ESPs that host **click-tracking links on their own domains** are also exposed.
- **List hygiene**: NHI produces false "engagement". List cleaning based on last activity **can keep addresses on the list that were only ever "active" because of NHI**, which defeats re-engagement series and policies for removing unengaged addresses ([List Hygiene & Sunset Policies](https://emailmarketing.net/learn/operations/list-hygiene-and-sunset-policies)).
- **Harm to recipients**: NHI may trigger actions the recipient never agreed to, such as completing a double or confirmed opt-in, confirming details, joining a new list, leaving a current list, or registering interest in items they do not care about. The result is more unwanted mail, abuse complaints and damage to the brand.

## Best practices that reduce NHI (from the research)

- **Use HTTPS for every link.** Tracking links that mix secure and non-secure addresses appear to be targeted disproportionately. An HTTP advertiser link behind an HTTPS tracking link "seems to trigger the most unwanted behavior."
- **Send separate campaigns to confirmed engaged recipients and to non-engaged recipients**, especially where inbox placement at certain domains is a problem.
- **Monitor content quality** at the level of links and beyond (for example, the ratio of images to text). "Aggressive" marketing, such as emoticons in subject lines or large catch words, tends to attract more NHI.
- **Sender reputation matters**: NHI is considerably lower for senders whose recipients are highly engaged.

The standing guidance also applies. Follow the [Senders BCP](https://emailmarketing.net/learn/industry-best-practices/m3aawg-senders-bcp) for deliverability and engagement, and the [Email Authentication BCP](https://emailmarketing.net/learn/industry-best-practices/m3aawg-email-authentication-bcp), which lets providers attach reputation to the sender's brand. Good content practices reduce the impact of NHI.

Version 4.0 of the [M3AAWG Sender Best Common Practices](https://www.m3aawg.org/senderbcp) (August 2026) reads engagement the same way during domain warm-up. A sharp rise in opens or clicks can mean security filters are inspecting the mail more closely, while a fall can mean it is landing in the junk folder.

## Conclusions and limits

- There is **no definitive guide to mitigation**. The study's data covers only the interactions that could be identified as NHI, not 100% of it.
- Scanners use **simulated behavior designed to be indistinguishable from natural human interactions**. Identifying it is already very difficult and "will become nearly impossible in the future."
- Removing NHI changes the numbers, but a sender can never be sure it caught everything, and the effort may not be worth it. If every ESP filters NHI differently, metrics become even harder to compare.
- In short, NHI has measurable and significant consequences. Re-evaluate how you use engagement data to decide mailing frequency or segmentation, and allow for the inflation when you read click and open dashboards.