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. It's the foundation of product-led growth email and the key to effective SaaS behavioral email marketing. 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. For a deeper look at building these sequences, check our guide on how to send emails based on product events.

Why Event-Based Matters More Than Ever

The shift to event-based email isn't just about personalization. It's about relevance and timing.

Relevance: A time-based email that says "Have you tried our reporting feature?" is irrelevant if the user already uses it daily. An event-based email that says "Great, you've created 10 reports! Here's how to schedule them automatically" is relevant because it's triggered by what the user actually did.

Timing: The best moment to send an email about a feature is right after the user shows interest in that feature's domain, not 7 days after signup when you've scheduled it. Event-based timing ensures emails arrive when they're most useful.

Efficiency: Event-based automation means you write fewer emails that serve more users. Instead of writing 20 time-based emails hoping to cover every scenario, you write 10 event-based emails that fire at exactly the right moment for each user.

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.

The event API is straightforward: one HTTP call with an event name, subscriber identifier, and optional properties. No SDK installation, no event schema definition, no data mapping. Send an event, and it's immediately available as a sequence trigger. For a startup that wants event-based email working this week, this simplicity matters.

Sequenzy also supports "inactivity events," which trigger when a user hasn't performed a specific action within a time window. "No login for 7 days" or "no project created in 14 days" can start re-engagement sequences. This addresses the common gap in event-based systems: responding not just to what users do, but to what they don't do.

The Stripe integration deserves emphasis. Payment events (trial started, payment succeeded, payment failed, subscription upgraded, subscription cancelled) flow in automatically without any code. Combined with your custom product events, this gives you a complete behavioral picture, both what users do in your product and what happens with their billing.

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, inactivity triggers 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.

The event data model in Customer.io is the most sophisticated in the email tool space. Events carry properties (key-value pairs), and you can use those properties in branching conditions, email personalization, and segment definitions. An event like "order.placed" with properties like "amount: 99, productName: Dashboard, planType: annual" gives you everything you need for targeted follow-up emails.

Customer.io also supports "event frequency" conditions: "user who triggered 'feature.used' more than 10 times in the last 30 days." This is crucial for identifying power users, detecting engagement trends, and building sophisticated subscriber segmentation based on usage intensity rather than just occurrence.

The "wait for event" step in workflows is uniquely powerful. The workflow pauses until a specific event occurs, then continues. This enables patterns like: "send onboarding email 1, wait for 'setup.completed', then send onboarding email 2." If the user completes setup in 1 hour, they get email 2 in 1 hour. If it takes 3 days, they get it in 3 days. The workflow adapts to the user's pace automatically.

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, frequency conditions 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.

The developer experience is the standout. The API documentation is clear, the SDKs are well-maintained, and you can go from reading the docs to sending your first event-triggered email in under an hour. For developer-focused teams (common in the PLG space), this matters more than having 50 workflow features you won't use.

The limitation is clear: no branching. You can't build "if user did X, send email A; otherwise, send email B." Each event triggers a specific sequence, period. For more nuanced automation, you'd need to handle the logic in your application code (sending different events based on conditions) rather than in the email tool. This works fine at small scale but becomes unwieldy as your automation needs grow.

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, excellent docs 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.

The "hold until" feature is Iterable's event-based standout. A workflow step can hold a user until a specific event occurs or a condition is met. "Hold until user opens the email" followed by a branch based on what they clicked gives you sophisticated event-response patterns across channels. Combined with the cross-channel capability, this enables sequences like: "send email, hold until opened or 24 hours pass, if not opened send push, hold until clicked or 12 hours pass, if not clicked send SMS."

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, hold-until 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.

Braze's "action-based delivery" is real-time event triggering at scale. When an event fires, the associated campaign or canvas step executes within seconds, even when processing millions of events per day. This real-time responsiveness is essential for time-sensitive triggers like abandoned cart recovery, feature-gate responses, and in-the-moment upgrade prompts.

The event analysis tools are also enterprise-grade. You can see event volume trends, correlations between events and conversions, and the impact of event-triggered messages on downstream metrics. This analytical layer helps you understand not just what events are happening, but which event-triggered emails are actually driving results.

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, event analytics 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.

Vero's approach to event data is clean. Events are first-class objects in the platform, not an afterthought bolted onto a list-based email tool. The event history for each user is visible and searchable, making it easy to understand a user's journey and debug automation logic. When you're troubleshooting why a specific user didn't receive an expected email, being able to see their complete event timeline is invaluable.

The SQL-based segmentation (mentioned in our PLG email tools guide) extends to event-based targeting. Data teams can write SQL queries against event data to define targeting conditions that would be impossible to express in a visual segment builder.

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, event timeline 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.

The event + CRM combination enables sophisticated patterns for sales-assisted PLG. When a product event indicates a user is a PQL (e.g., "team.invited" with property "teamSize: 10+"), the automation can check the CRM for existing deal data, and then either trigger an automated upgrade sequence or create a task for the sales team, based on the deal context. This bridges the gap between product-led and sales-assisted growth motions.

ActiveCampaign's Zapier integration also means you can pipe events from tools that don't have direct integrations. If your analytics tool (Mixpanel, Amplitude) detects a behavioral pattern, Zapier can send that as an event to ActiveCampaign. This extends the event-based model to data sources beyond your own product.

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, Zapier events 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

A consistent naming convention pays dividends as your event count grows. When you have 30 events, being able to predict the name ("it's probably report.created") saves time and prevents the confusion of similar-but-different event names.

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" }
feature.used should include { featureName: "Reports", usageCount: 5 }

Properties enable dynamic email content. "You created {{projectName}}" is more personal than "You created a project." Properties also enable branching: route users to different emails based on the plan type, feature name, or amount in the event properties.

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)
Payment events (trial started, payment succeeded, payment failed)

A good rule of thumb: if an event doesn't trigger an email, update a subscriber attribute, or contribute to a segment filter, don't send it to your email tool. You can always add events later, but removing noisy events is harder.

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

For critical events like payment failures or trial expirations, test both the happy path and edge cases. What happens if the event fires twice? What if the subscriber doesn't exist yet? What if the event properties are missing?

Monitor Event Volume

Track your event volume over time. Sudden spikes might indicate a bug (an event firing in a loop). Sudden drops might indicate a broken integration. Most email tools show event volume in their dashboards, but setting up alerts for unusual patterns is worth the effort for production systems.

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. Pairs well with a complete lifecycle strategy.

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. Check your tool's re-entry settings to make sure this is configured correctly.

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. The best tools (Customer.io, Braze) support "wait for event" steps that pause the workflow until a specific event occurs, with a timeout fallback.

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. For mission-critical events (payment failures, security alerts), consider a message queue (like Redis or RabbitMQ) between your application and the email tool as a buffer.

How do I debug event-based automations? Start with the event timeline for a specific user. Most tools show which events a user has triggered, when they triggered them, and which automations those events activated. If an expected email wasn't sent, trace the chain: was the event received? Did it match the trigger condition? Was the user already in the automation? Did they meet the branch conditions? Systematic debugging through the chain usually identifies the issue quickly.

Should I send events from the client side or server side? Server side, always, for email automation events. Client-side events (from JavaScript in the browser) are unreliable due to ad blockers, browser extensions, and network issues. Server-side events are reliable and secure. Send events from your backend when database state changes (user created, project saved, payment processed) rather than from the frontend when UI actions occur.

How do I handle events for users who aren't yet subscribers? Most event-based tools support "identifying" a user before they become a subscriber. When an anonymous user triggers an event, it's stored and associated with their profile once they identify (usually at signup). This means pre-signup events can influence post-signup automations. For example, if a user visits the pricing page 3 times before signing up, that context can shape the onboarding sequence they receive.

What's the latency for event-based email triggering? Most tools process events and trigger emails within seconds to minutes. Customer.io and Braze process events in near real-time (seconds). Sequenzy and Loops typically process within minutes. For most SaaS use cases, minutes-level latency is fine. For time-critical triggers (like abandoned cart or real-time security alerts), confirm your tool's processing time meets your requirements.