Picture a segment called Webinar sign-ups: everyone who registered for your Thursday webinar. On Monday it has 900 people. On Thursday, 1,200. On Friday, after the webinar is over, someone else signs up on the page you forgot to take down: now it's 1,214.
The segment isn't broken. A segment is a rule, not a list: who meets the condition today. That's why what matters is how you use it.
Two ways to use a segment
As a snapshot. Boom reads the segment once and sends to whoever is in it at that moment. Anyone who joins later gets nothing. That's how a campaign works: you can have it read the segment at send time (the default: someone who already left the segment, say because they bought, doesn't get it) or now, when you schedule it.
As a trigger. A journey whose entry is a Segment ("Automatically enroll when a customer enters a segment") enrolls every person who enters the segment, from the moment you publish until you stop it. When you publish, the Include existing members box also adds whoever was already in.
Both are useful. The problem is using the second one thinking it's the first.
The trap
You build a journey with Webinar sign-ups as its entry, tick Include existing members and publish. That day 1,200 invitations go out, then the reminder, then "we start in an hour". It looks exactly like a one-time send.
But the trigger keeps listening. On Friday, person 1,213 signs up and gets "see you tomorrow" for a webinar that was yesterday. On Saturday, another. Nobody notices, because the first day went out perfectly and the report looks fine.
The box says what happens to people who are already in. It says nothing about people who will arrive, and people who arrive always get it.
How to tell which one you have
- Open the initiative and go to Journey. Look at the entry node: if it says Segment, it's a live trigger. If it says Manual, nobody enters on their own.
- Go to Executions and sort by date. If there are enrollments from days after your send, the segment is still enrolling.
- If you created it from Campaigns with the campaign form, it's a snapshot: it sends once and closes on its own when the conversations end.
How to stop it
If you found a live trigger that was meant to be a one-time send, Pause enrollment on the initiative stops new enrollments. Conversations that already started carry on.
Next time, decide before you build anything:
- Once, to whoever is there today: a campaign with the segment as its audience.
- To each person as they arrive: an initiative with a Segment entry. Decide on purpose whether you tick Include existing members.
A limit that helps either way
On the entry node, Enrollment limits (optional) controls how many times the same person can enter: Max enrollments Per window. With 1 and the longest window, someone who leaves the segment and comes back doesn't get the message twice. It doesn't stop new people, but it keeps the same person from getting it again.
A short rule
If the message has an expiry date, like an event, a promotion or a notice, use the segment as a snapshot. If the message is part of how you treat anyone who reaches that point, use it as a trigger. And if you're not sure which one you have, the date column in Executions tells you in ten seconds.
The full campaigns reference is in our documentation.
