How do spam-filter tests open and click links automatically?

Before your email reaches a recipient, many corporate and ISP spam filters run it through a sandbox. That sandbox opens the message, loads every image, and clicks every link, all automatically, to check whether anything suspicious happens.

The logic is straightforward: if a link redirects to a known phishing site, downloads a file, or triggers suspicious JavaScript behavior, the filter catches it before a human ever sees the email. For security purposes, this is great. For your engagement metrics, it's a source of noise.

What makes sandbox clicks look different from human clicks: they happen within milliseconds of delivery, they click every link in the message (not just the ones a human would find interesting), they come from IP ranges associated with cloud providers and data centers, and they sometimes hit unsubscribe links and preference centers.

That last one is worth noting. If your unsubscribe process is a single-click action, security scanners can accidentally trigger unsubscribes. Most senders protect against this with a two-step confirmation page, partly for this reason.

The problem compounds for B2B senders. Corporate environments often run all inbound email through Proofpoint, Mimecast, or Microsoft's filtering, all of which scan links aggressively. If your list skews toward business email domains, your click-through rates may be meaningfully inflated.

For the full picture on other sources of fake engagement, see how bots and spam-checkers distort metrics generally and the guide on identifying fake engagement. Both cover detection methods you can apply in your own analytics.