A few things to check on our side:
- Is reply detection actually enabled on the campaign itself? It's a per-campaign setting under Campaign > Settings > Reply Detection — it's off by default for campaigns created before we added the feature.
- Is the mailbox you're sending from actually connected for reply tracking (not just sending)? Sending and reply-detection are separate connections in Settings > Sending.
If reply detection is enabled and the mailbox is connected, replies should show up in your SubsiMail inbox within a couple of minutes, which is what triggers the Zapier webhook.