How can I create a segment of users who did not open a specific email campaign?

You can build this audience in the Segment Builder using the default PW_EmailOpen event with the never condition.

Steps

1. Go to Audience → Segments in the Control Panel and create a new segment.
2. Click Add filter by → Event and select PW_EmailOpen.
3. Set the condition to never and specify a timeframe (for example, during the last 30 days) — a timeframe is required.
4. To restrict the check to one campaign, add a condition on the event attribute message_code (or message_id) with the code of the email you sent.
5. Save the segment.

The resulting logic reads: PW_EmailOpen → never → message_code = <your message code>, i.e. users who were sent that email but produced no open event.

Tip — a faster route for a simple re-send: open the email in Message History, click the message name to open its detailed statistics and use Resend to non-openers. The option is unavailable while the original campaign is still running or if there are no non-openers.

Note on open tracking: PW_EmailOpen carries an opened_by attribute — user for a genuine open and ampp for an automated Apple Mail Privacy Protection pre-fetch. Filter on opened_by = user if you want automated opens to be treated as “not opened”.