Every email automation starts with the same question, and it isn't "what do I write?". It's "what has to happen for this to go out?". You answer it by choosing a trigger, and in arrobaMail three of them start conversations: someone subscribes through a form, your system announces that something happened, or the contact reacts to an email you already sent.
Choosing well among those three is, without exaggeration, 80% of the work. You can rewrite the copy whenever you want; you can change the waits in ten seconds. But the wrong trigger means the flow never runs — and the worst part is that it raises no error anywhere. You saved it, you activated it, it all looks right, and nobody enters. Ever.
This piece is the map. By the end you'll know which one is yours, and you'll have the step-by-step for each.
The three front doors
1. The form: when people subscribe on their own
This is the best-known door and the one with the best return. You put a form on your site, someone leaves their email, confirms, and a welcome sequence begins. They get a first email introducing your brand and, a few days later, another with the most useful thing you have to offer.
It works so well for one reason: timing. Right after someone signs up is when they're paying you the most attention. If you let three weeks go by until your next campaign, that interest has cooled. The automated welcome catches it while it's warm, and it does so while you sleep.
There's one detail that confuses almost everyone the first time, and it's worth knowing up front: the trigger fires when the person confirms, not when they submit the form. arrobaMail uses double opt-in, so between "Subscribe" and the start of the flow there's an intermediate step that depends on the subscriber. If you're testing and see no movement, that's almost always it: the confirmation is missing.
And even when it feels like friction, it's one of the best things that can happen to your list. It filters out mistyped addresses, blocks bot sign-ups, and leaves only people who actually wanted to be there. Better opens, fewer bounces, healthier sending reputation. It's the difference between a big list and a list that lands.
→ The full walkthrough: automate your welcome from a form.
2. The API event: when your system is the one announcing
This, for us, is the most interesting part of all of it — and the one people most underestimate.
If your own system creates the contacts — your e-commerce, your back office, your app — the subscription trigger is no use, because it's waiting for an opt-in your backend never produces. The answer is the custom event: your system tells arrobaMail "this happened" with a single HTTP call, and the flow starts.
Think about what that enables. A confirmed purchase fires the thank-you with related products. A trial expiring in three days fires the conversion sequence. A plan change fires onboarding for the new features. A form on your own site, a webhook from your payment gateway, a button in your back office: anything your system knows can start an email conversation, without anyone in marketing having to find out or press anything.
And the division of labor lands exactly where it should: your system owns the data and arrobaMail owns the conversation. If tomorrow you want to add a third email to the sequence, stretch a wait from 7 to 10 days, or rewrite the subject line, you do it in the visual editor — without touching a line of code or deploying anything. That separation is what turns an afternoon's integration into something that then runs on its own for years.
Two rules and it's working: the event fires but doesn't create (the contact has to exist on the list, so sign-up first, event second) and the call comes from your backend, never from the visitor's browser.
→ The full walkthrough, with the example call: trigger automations from your system via API.
3. Behavior: when it reacts to what each person did
The third door doesn't wait for anyone to subscribe or for your system to announce anything. It listens to what each contact does with the emails you already sent.
You send a launch campaign. Instead of treating everyone the same, the flow splits in two: whoever clicked the product link immediately gets the expanded information and an offer; whoever never opened gets a reminder with a different subject a few days later. Same send, two different conversations.
This can be used in two ways, and the difference matters: as a trigger, so a click starts a brand-new flow; or as a condition, to branch a flow that was already running. The rule for choosing is a single question: is the person already inside the flow? If not, trigger. If so, condition.
One level of precision that tends to surprise people: the click trigger lets you pick which link. If your campaign has "see plans", "read the case study" and "talk to sales", you can build a different flow for each — because each click says something different about what that person is thinking. Whoever went to see plans is much closer to buying than whoever went to read a case study, and deserves a different message.
One caveat: a click is worth far more than an open. Opening says "the subject line caught my eye"; clicking says "I'm interested". Use opens for soft logic and save clicks for the decisions that matter.
→ The full walkthrough: automate based on opens and clicks.
So, which one is yours?
| If your situation is… | Your trigger is | Start with |
|---|---|---|
| I have a form on my site and want to welcome subscribers properly | Subscription | welcome from a form |
| My system already knows when someone buys, signs up, or lets a plan expire | Custom event | firing through the API |
| I already send campaigns and want to follow up differently based on what people did | Open / Click | automating by behavior |
The honest answer, for most people, is all three, in that order. The welcome flow pays back the invested time fastest and needs no technical help. Behavior is the natural next step, because it makes use of campaigns you're already sending. And the API event is the one that opens the big door, once you have a system of your own on the other side.
You don't have to pick just one, or do them all in the same month. Each is an independent flow that builds on the last.
What you're actually buying
It's worth saying plainly, because it gets lost among the technical details: an automation is built once and works forever. It isn't a campaign you send and it's over. It's a decision you make one afternoon that keeps executing — for every person, on their own schedule, at three in the morning on a Sunday — without you intervening again.
That's the real change. You go from "I didn't get around to the newsletter this week" to the relationship with each contact advancing on its own while you do something else. And since everything is measured, the dashboard keeps telling you how many took each branch, where people drop off, and which email performs best — so the flow you built this month is better next month.
If you want the technical reference for all five triggers — the three in this piece plus unsubscription, and the behavior conditions — it's all in automation triggers. And if you're curious how far this goes, there's a fourth path that no longer goes through any dashboard at all: your AI assistant operating your account over MCP.
Don't have an account yet? Try arrobaMail for free and build your first automation today: the welcome flow takes less time than it took you to read this.