# Open and click tracking

Source: https://catalystgroup.gg/docs/email-delivery/open-and-click-tracking/
Updated: 2026-10-19 · By Duane Garner

How CRM-NG SMTP counts opens and clicks in HTML emails, what unique and total mean, the privacy trade-offs, and when tracking is switched off.

CRM-NG SMTP can count how often your HTML emails are opened and how often their links are clicked. This article explains how that works, how to read the numbers, and what to consider before turning it on. It is for site owners who want a rough idea of engagement with their site's emails.

 

All tracking data stays in your own WordPress database.

 

## Turn it on

 

Go to **CRM-NG SMTP → Settings → Email Log** and tick **Enabled** next to either or both of:

 
- **Track HTML email opens**
- **Track clicks in HTML email links**

 

Press **Save Local Logging Settings**. **Enable local email logging** must also be on, because counts are attached to log entries.

 

Tracking only applies to emails sent after you turn it on, and only to HTML emails. Plain-text emails, which include many WordPress core messages, cannot be tracked.

 

## How open tracking works

 

When an HTML email is sent, CRM-NG SMTP adds a tiny, invisible 1×1 pixel image to the end of the message. The image lives on your own site. When the recipient's mail program loads images, it requests that pixel, and your site counts an open.

 

## How click tracking works

 

CRM-NG SMTP rewrites every `http://` and `https://` link in the HTML so that it points to your site first. When someone clicks, your site counts the click and immediately sends them on to the original address. The visitor barely notices the extra step.

 

Each tracking address carries a signature made from your site's secret keys. If anyone edits a tracking link, for example to send people to a different site, the signature no longer matches and your site refuses the request. This stops your domain being used as an open redirect.

 

> **Links keep working after cleanup:** Tracked links keep redirecting even after the log entry has been deleted by the retention cleanup. The click is simply not counted. If your WordPress security keys (the salts in `wp-config.php`) are changed, older tracked links stop working, because their signatures no longer match.

 

## Unique versus total

 

| Figure | How it is counted | Where you see it |
| --- | --- | --- |
| Unique opens / clicks | Once per combination of device or mail program and link. Opening the same email ten times on one phone counts once. | The Unique opens / clicks column in the log, the Email reports screen, the weekly summary and the dashboard widget |
| Total opens and clicks | Every request, including repeat opens | The Opens and Clicks columns of the CSV export |

 

The **Email Reports** screen puts it this way: **Engagement columns show unique client/link combinations; total requests remain available in individual log details.**

 

## Why the numbers are never exact

 

Treat open and click counts as a trend, not a fact.

 
- **Images turned off.** Many people and many workplaces block images by default. Those opens are never counted.
- **Privacy features.** Some mail apps download every image as soon as a message arrives, whether or not it is read. This counts opens that did not happen.
- **Security scanners.** Company mail filters often follow every link to check it is safe. This counts clicks that no person made.
- **Plain-text mail.** Plain-text emails are never tracked.

 

## Privacy considerations

 

Tracking tells you something about what a person did with your email. Before turning it on:

 
- Make sure your privacy policy says you measure opens and clicks.
- Consider whether you need it at all for transactional email such as password resets and receipts.
- Know what is stored: the time of each open or click, the link clicked, and the mail program's identifying text (its user agent). IP addresses are not stored.
- Tracking records are deleted with their log entry, by the daily cleanup or when you delete entries.

 

## When CRM-NG campaigns turn it off

 

If you also use the CRM-NG marketing campaigns feature, campaigns have their own tracking and unsubscribe handling. While a campaign is sending, CRM-NG SMTP's open and click tracking is switched off for those messages, so links are not rewritten twice and each open is counted once, in the campaign's own reports. Your normal site emails are tracked as usual.

 

## Related

 
- [Setting up the email log](https://catalystgroup.gg/docs/email-delivery/email-log-setup/)
- [Email reports](https://catalystgroup.gg/docs/email-delivery/email-reports/)
- [Viewing the email log](https://catalystgroup.gg/docs/email-delivery/viewing-the-email-log/)
- [What the plugin stores and sends](https://catalystgroup.gg/docs/email-delivery/privacy-and-data/)
- [Using CRM-NG SMTP with the CRM-NG family](https://catalystgroup.gg/docs/email-delivery/using-with-crm-ng/)