The right replacement depends on what your messaging is built around. SaaS email tools, developer notification platforms, push-first services, deliverability-led senders and all-in-one suites all overlap with an event-driven engagement platform, but each centres on something different. Rebuild one live journey and compare billing units before you choose.
The emails are the easy bit to move. Customer.io is built around event data your product sends, feeding journeys across email, push, SMS and in-app messages. So when you leave, the real work is rebuilding the tracking, the segments and the journeys that run off it, not copying templates across.
Keep that in mind as you read the nine tools below. They're listed in no particular order and grouped by what each one is built around, because that decides how much of your setup carries over.
Built around what?
Email for SaaS teams. Userlist, Encharge and Loops are made for software businesses. One tracks company accounts with several users each, one leans on behaviour-based automation with a HubSpot sync, and one keeps marketing, product and transactional email on a single contact record.
Developer infrastructure. Courier and Knock are for engineers who want notifications defined in code and routed across email, push, SMS, chat and in-app feeds, with journeys and user preferences handled for them.
Push first. OneSignal starts from mobile and web push and adds SMS, email and in-app messages around it. It's the natural fit when your app's home screen is your main channel.
Deliverability first. Bento checks and paces every send and publishes its delivery rates, which suits senders who've had inbox trouble before.
Product-led journeys. Vero sends email, push and SMS based on what people do in your product. Of the nine, it's the closest in shape to an event-driven setup.
All in one. Brevo bundles email, SMS, WhatsApp, chat and a CRM, which suits a small business more than a product team with complex event data.
Check the billing unit before you compare
Before you compare plans, find out what each tool counts, because it won't always be what you'd expect. Some bill by contacts or profiles, some by the number of sends, and some by active users or notifications delivered. The same audience can land in very different tiers across them.
Work out your own numbers first: how many profiles you store, how many are active in a typical month, and how many messages you send. Then ask each vendor which of those it bills on, and get the answer in writing so there's no surprise later. A tool that looks generous on one count can surprise you on another.
Side-by-side view
| Tool | Centre of the product | Strongest fit |
|---|---|---|
| Bento | Email with a deliverability focus | Senders who watch inbox placement |
| Brevo | All-in-one marketing and CRM | Email, SMS, WhatsApp and CRM together |
| Courier | Developer notification routing | Product notifications across many channels |
| Encharge | Behaviour-based automation for SaaS | Software teams that live in HubSpot |
| Knock | Developer messaging infrastructure | Lifecycle and transactional messages in code |
| Loops | SaaS email from one contact record | Marketing, product and transactional email together |
| OneSignal | Push-first multi-channel | Mobile and web push first |
| Userlist | B2B SaaS email with company accounts | B2B products sold to teams |
| Vero | Product-led multi-channel messaging | Messages triggered by product behaviour |
Who each tool suits
In alphabetical order, with no ranking.
Bento
Best for: Senders who care most about reaching the inbox, with campaigns, automations and transactional email where each send is checked and paced, and delivery rates published live.
Brevo
Best for: Small businesses that want email, SMS, WhatsApp, push, live chat and a CRM in one account rather than a dedicated product messaging tool.
Courier
Best for: Engineering teams routing product notifications across email, push, SMS and Slack through APIs and SDKs, with a visual journey builder and preferences built in.
Encharge
Best for: Growing SaaS businesses running behaviour-based email to nurture, convert and onboard users, with native forms and a two-way HubSpot sync.
Knock
Best for: Developers shipping cross-channel lifecycle and transactional messages, with an in-app feed and an agent step inside the workflow builder.
Loops
Best for: SaaS teams that want marketing, lifecycle and transactional email from one contact record, with an API an AI agent can use to set up workflows.
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OneSignal
Best for: Apps where push is the main channel, with web push, SMS, email and in-app messaging joined up in one journeys builder.
Userlist
Best for: B2B SaaS companies whose customers are teams, since it tracks company accounts with several users each, plus visual workflows and in-app messages.
Vero
Best for: Product-led teams sending email, mobile push and SMS based on what users do inside the product, with journeys, broadcasts and audiences.
My advice if your messages run on product events
If your messages are triggered by product events, start with the tools built around that: the SaaS email group, the product-led option, or developer infrastructure if engineers own messaging. If you mostly send newsletters and promotions with a few automations, an all-in-one suite will feel simpler, and you may not need event tracking at all.
Either way, ask for a test export of your own data before you commit. It's the quickest way to see what you'd be carrying over. My guide to customer engagement platforms covers the bigger suites, and my onboarding email drip template is a good first journey to rebuild.
Rebuild one journey before you sign
Pick the journey that matters most, which is usually onboarding, and rebuild it in your top choice during the trial. Send the same events, recreate the segment and the timing, and check the messages arrive when they should.
If that one journey takes a day, the full move is manageable. If it takes a week because events don't map cleanly, you've learned that before signing anything. Keep your old account running until the new journeys have sent real messages to real people.
And check consent carries across. Rules on marketing permission vary by country, so confirm with the regulator where you operate before importing contacts.
Do you make an email, push or customer messaging tool? Tool makers can ask to be considered for a featured place on this list.
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Frequently asked questions
What's the hardest part of leaving Customer.io?
Rebuilding event tracking, segments and journeys. Templates move easily enough, but the logic behind who gets what and when has to be recreated in the new tool.
How do messaging tools bill differently?
Some count contacts or profiles, some count sends, and some count active users or notifications. Check which unit each uses against your own audience before comparing plans.
Is a developer notification platform a replacement for marketing email?
Partly. Notification platforms are built for product and transactional messages defined in code. Many teams pair one with a marketing tool rather than using it for newsletters.
Can I keep transactional and marketing email in one tool?
Yes. Several tools here send both from the same contact record, which keeps preferences and history in one place.
Do I need to re-collect consent when I switch?
Not always, but you need records of how each contact opted in. Rules vary by country, so check the guidance from the regulator where you operate.
