You sent a campaign through Bonzo. The open rate came back at 45%. Feels great — until you follow up with those "openers" and half of them aren't familiar with your email.
Sound familiar? You're not imagining things. Email open tracking has a fundamental reliability problem, and understanding it will make you a sharper marketer.
How Open Tracking Works
When you send an email through Bonzo (or any email platform), a tiny invisible image — called a tracking pixel — is embedded in the message. It's typically a 1x1 transparent PNG, invisible to the naked eye. When the email is opened and images load, that pixel sends a signal back to Bonzo's servers: someone opened this.
Simple, elegant, and not always reliable.
Why "Opened" Doesn't Always Mean Opened
Several things can fire that pixel without your contact actually seeing the email:
1. Apple Mail Privacy Protection (The Big One)
In September 2021, Apple introduced Mail Privacy Protection (MPP) with iOS 15 and macOS Monterey. The impact was seismic.
When MPP is enabled — and it's on by default for most Apple Mail users — Apple routes all email content through its own proxy servers and pre-loads every image in every email the moment it arrives, regardless of whether the recipient opens it. From Bonzo's perspective, that looks like an open.
Roughly 50–60% of all emails are opened on Apple devices. That means a huge portion of your list is likely triggering ghost opens automatically.
2. Corporate Email Security Scanners
Many companies run their employees' email through security gateways — tools like Proofpoint, Mimecast, or Barracuda. These systems automatically scan incoming emails for phishing links and malicious content, which means they follow links and load images, including your tracking pixel, before the email ever reaches the inbox.
If you're marketing to professionals at larger companies, this is a real factor.
3. Gmail's Image Caching
Google routes all images in Gmail through its own proxy servers. While this doesn't pre-load images before opening, it does mean the open is logged at Google's cache level rather than at the moment your contact interacts with the email — which can introduce timing inaccuracies.
4. Preview Panes
Some email clients load a preview of an email — including images — in a side or bottom pane without the user ever clicking to open it. Depending on how the client handles that preview, it can fire the tracking pixel even though your contact never consciously chose to read your message.
What You Should Do Instead
None of this means email marketing is broken — it means you need to shift what you measure.
Make Clicks Your North Star
A click requires a human to make a deliberate choice. It can't be faked by a proxy or a security scanner. If someone clicks a link in your Bonzo email, they were there. Weight click-through rate (CTR) and click-to-open rate (CTOR) far more heavily than raw open rate when judging campaign performance.
Watch for Multiple Opens
The Bonzo system will track and report the number of opens it's seen for the same email message. A single open may just be a security scanner, but several opens on the same message is more indicative of a consumer that has engaged with your content and is returning to it multiple times.
Track Replies and Conversations
In real estate, a reply is worth more than any metric. Replies signal genuine interest, and they can't be automated. Look at how many contacts reply or book a call — that's your real engagement signal.
Use Opens as a Directional Signal, Not a Fact
Open rate still has value — just treat it as a trend indicator. If your open rate drops from 30% to 10% over two campaigns, something changed (subject line, send time, list health). Don't obsess over the absolute number; watch the direction.
A/B Test Subject Lines with Caution
Subject line A/B tests based purely on open rates are now less reliable than they used to be. When possible, let the test run long enough that click data can inform the winner, not just opens.
Keep Your List Clean
Ghost opens can mask a decaying list. A contact who hasn't clicked anything in six months is almost certainly disengaged, even if they show as an "opener." Regularly sunset contacts who haven't clicked or replied in 90–180 days to protect your deliverability.
The Bottom Line
Email open tracking was always a proxy metric — a best guess, not a certainty. The rise of Apple MPP and corporate security tools has made that gap between "reported open" and "actual human eyeballs" much wider. The good news is that Bonzo gives you richer signals to work with: clicks, replies, booked meetings, and pipeline activity. Lean on those. The agents who stop chasing open rates and start measuring real engagement are the ones who build sequences that actually convert.
Have questions about how to interpret your Bonzo campaign metrics? Reach out to the Bonzo support team or check the Help Center for guidance on reading your analytics dashboard.