Most email automation is time-based. "Send email 3 days after signup." "Wait 7 days, then send follow-up." This works for simple sequences, but it ignores what the user is actually doing. A user who completes onboarding in 2 hours doesn't need the same emails as a user who hasn't logged in for a week.

Event-based email automation triggers on user actions, not arbitrary timers. When a user completes a step, triggers an event. When they hit a milestone, triggers a different event. When they stop doing something (inactivity), that's an event too. Your email tool listens for these events and responds accordingly.

This is how the best SaaS companies do email. Here's which tools handle event-based automation best.

What Event-Based Email Automation Looks Like

Instead of:

Day 0: Welcome email
Day 3: Feature introduction
Day 7: Upgrade prompt

You get:

Event "signup.completed": Welcome email
Event "first_project.created": Feature deep-dive email
No event for 3 days: Re-engagement email
Event "trial.ending" (from Stripe): Conversion email

The emails adapt to user behavior rather than following a fixed schedule. Users who move fast get relevant content faster. Users who are stuck get help when they need it.

The 7 Best Options

1. Sequenzy

Best for: SaaS founders wanting event-driven lifecycle email without complexity

Sequenzy's automation model is event-driven by design. Send an event to Sequenzy's API when a user takes an action, and Sequenzy triggers the appropriate sequence. Events like "signup.completed," "trial.ending," or custom product events start automated email sequences.

The key difference from Customer.io is simplicity. Sequenzy gives you event-triggered sequences with built-in SaaS workflows (onboarding, dunning, churn prevention) rather than a blank-canvas workflow builder. You get the event-based approach without building complex branching logic. The Stripe integration automatically generates payment events, so you only need to manually track product usage events.

Event handling: Custom events via API, automatic Stripe events, inactivity triggers, tag-based triggers Pricing: From $29/month Pros: Event-driven by design, SaaS-specific workflows, Stripe automation, simple setup Cons: Less flexible than Customer.io for complex branching, newer platform

2. Customer.io

Best for: The most powerful event-based automation engine

Customer.io was built around events. Every automation starts with an event trigger: a custom event from your application, a page view, a segment membership change, or an attribute update. The automation builder lets you branch on event properties, wait for specific events, and combine multiple event conditions.

You can build automations like "when user triggers 'project.created' AND has attribute 'plan' = 'trial' AND has NOT triggered 'invite.sent' within 7 days, send team collaboration email." This level of event-based logic is unmatched.

Event handling: Custom events with properties, event combinations, event absence (inactivity), attribute-based triggers Pricing: From $100/month Pros: Most powerful event-based automation, flexible branching, event combinations, mature Cons: Expensive, steep learning curve, can be overengineered

3. Loops

Best for: Startups wanting simple event-to-email automation

Loops is built around events. You send events via API, and those events trigger email sequences. The model is deliberately simple: event fires, sequence starts. There's no complex branching or multi-condition triggers. For early-stage SaaS, this simplicity is the point.

Loops handles the basics well: user signed up (send welcome), user created project (send tips), user hasn't logged in (send re-engagement). If your automation needs fit "when X happens, send Y," Loops delivers without the overhead of a full automation builder.

Event handling: Custom events via API, basic event triggers, simple sequences Pricing: Free for 1,000 contacts, from $49/month Pros: Simple event model, developer-friendly, good free tier, fast setup Cons: No complex branching, basic event logic, limited to simple sequences

4. Iterable

Best for: Growth teams wanting event-based automation across channels

Iterable's Studio (their workflow builder) triggers on custom events and supports complex event-based logic across email, push, SMS, and in-app messaging. Events from your application trigger workflows that can branch based on event properties, user attributes, and channel engagement.

For growth teams that need event-based automation beyond just email, Iterable handles the cross-channel piece. An event can trigger an email, and if the user doesn't engage, follow up with a push notification or in-app message. The event model supports properties, making it easy to personalize messages based on what happened.

Event handling: Custom events with properties, cross-channel triggers, workflow branching, event-based exits Pricing: Custom (typically $500+/month) Pros: Cross-channel, visual workflow builder, event properties, growth-focused Cons: Custom pricing, mid-market complexity, learning curve

5. Braze

Best for: Enterprise teams with complex event-based orchestration

Braze's Canvas (workflow builder) handles event-based automation at enterprise scale. Custom events trigger campaigns, canvases can branch on event properties, and the platform supports real-time event processing across millions of users.

The event model is sophisticated: trigger on event occurrence, event frequency (user did X more than 3 times), event recency (user did X within last 24 hours), and event absence (user has not done X in 7 days). For enterprise teams with complex event-based needs, Braze has the depth.

Event handling: Custom events, event frequency, event recency, event absence, real-time at scale Pricing: Custom (typically $50K+/year) Pros: Enterprise-scale event processing, sophisticated triggers, multi-channel, real-time Cons: Enterprise pricing, complex, requires dedicated team

6. Vero

Best for: Event-based email for mid-market product teams

Vero is built around behavioral triggers. Events from your application drive automated email campaigns. The platform tracks user behavior and lets you build automations based on event occurrence, event properties, and user attributes.

Vero sits between the simplicity of Loops and the complexity of Customer.io. You get event-based triggers with reasonable branching and segmentation, without needing to build enterprise-grade workflows. For mid-market product teams, it's a solid middle ground.

Event handling: Custom events via API, behavioral triggers, event properties, user attributes Pricing: From $54/month Pros: Event-focused design, good balance of power and simplicity, behavioral targeting Cons: Smaller ecosystem, less well-known, mid-market positioning

7. ActiveCampaign

Best for: Teams wanting event-based automation with CRM integration

ActiveCampaign's automation builder supports event-based triggers through its API and native integrations. Custom events (sent via API or Zapier) can start automations, and the builder supports branching based on contact data, event properties, and engagement history.

The CRM integration adds context to event-based automations. When a product event fires, the automation can also check CRM data (deal stage, lead score) before deciding which email to send. For teams that combine product analytics with sales data, this cross-referencing is valuable.

Event handling: Custom events via API/Zapier, CRM-enriched triggers, automation builder Pricing: From $29/month Pros: CRM + event automation, powerful builder, broad integration ecosystem Cons: Event tracking requires API or Zapier, can feel complex, some features on higher tiers

Event Tracking Best Practices

Name Events Consistently

Use a consistent naming convention:

object.action format: project.created, user.upgraded, payment.failed
Past tense for completed actions: onboarding.completed not onboarding.complete
Lowercase with dots: feature.first_used not FeatureFirstUsed

Include Relevant Properties

Events should carry the data your email tool needs for personalization:

project.created should include { projectName: "My App", projectType: "web" }
payment.failed should include { amount: 49, currency: "USD", retryDate: "2026-02-20" }

Don't Over-Track

Send only events that trigger emails or update subscriber profiles. Your email tool doesn't need every button click or page view. Focus on:

Account lifecycle events (signup, upgrade, cancel, churn)
Product milestone events (first project, first invite, first export)
Engagement threshold events (power user, inactive for 7 days)

Test Event Flows

Before launching automations, test the full flow:

Trigger the event from your test environment
Verify the event arrives at your email tool
Confirm the automation triggers correctly
Check the email renders with the right personalization data
Verify the email delivers to the inbox

How to Choose

You need the most powerful event automation: Customer.io. Unmatched flexibility for complex event-based workflows.

You're SaaS and want event-driven lifecycle email: Sequenzy. Purpose-built for SaaS with automatic Stripe events.

You want simple event-to-email: Loops. Clean, developer-friendly, no complexity overhead.

You need cross-channel event automation: Iterable. Events driving email, push, SMS, and in-app.

You're enterprise scale: Braze. Sophisticated event processing for millions of users.

You want balanced event automation: Vero. Good middle ground between simple and complex.

You need event automation + CRM: ActiveCampaign. Events enriched with CRM context.

FAQ

What's the difference between event-based and trigger-based automation? They're essentially the same thing. "Event-based" usually implies custom events from your application (user actions). "Trigger-based" is broader and includes any automation start condition (time-based, segment-based, event-based). All event-based automations are trigger-based, but not all triggers are events.

How do I handle events that happen multiple times? Most event-based tools let you configure whether a user can re-enter an automation. For events like "project.created" (which can happen many times), you might want to trigger the automation only on the first occurrence. For events like "payment.failed," you want to trigger every time.

Can I combine events with time-based delays? Yes. Most event-based tools support hybrid workflows: trigger on an event, wait 24 hours, check if another event occurred, then branch. This gives you the responsiveness of events with the pacing of time-based sequences.

What happens if my app sends an event and the email tool is down? Good email tools queue events and process them when back online. For critical events, implement retry logic in your application. Most platforms have 99.9%+ uptime, so this is rarely an issue in practice.