Customer.io vs Mailchimp for SaaS (2026): Pricing, Features, and Where SendHeron Fits
Customer.io and Mailchimp compared for SaaS lifecycle email in 2026: what each costs at 5,000 and 40,000 contacts, what counts as a contact, how automation and transactional email differ, and where SendHeron fits and does not.
On this page (23)
Search "Customer.io vs Mailchimp" and most of what comes back lines the two up in a feature grid. The more useful fact is the price: at the list sizes most SaaS products pass through, the two cost almost exactly the same. So money does not decide this one. The model does. Customer.io sends messages when your product says something happened, and Mailchimp sends campaigns to an audience you collect. We build a third option, SendHeron, so this article also says where it fits and, just as plainly, where it does not.
Prices below are as of October 14, 2026, on monthly billing, from each vendor's own pricing page: Customer.io and Mailchimp in US dollars, SendHeron in euros. Prices change, so check before you decide.
What you will learn
- What each tool charges at 5,000 and at 40,000 contacts, and what it counts as a contact
- How automation and transactional email differ, which matters more than the headline price
- Which channels each one is built around
- A plain recommendation per situation, including the situations where SendHeron is the wrong pick
Quick comparison
| Customer.io | Mailchimp | SendHeron | |
|---|---|---|---|
| Built for | Data-driven messaging across email, push, in-app and SMS | Email marketing and campaigns for a broad range of businesses | SaaS lifecycle and transactional email |
| Priced on | Profiles, counting people and objects | Contacts, including unsubscribed ones | Subscribed contacts only |
| At 5,000 contacts | $100 a month (Essentials) | $100 a month (Standard) | €19 a month (Starter, up to 10,000) |
| Automation | Visual workflow builder | Up to 200 flows on Standard; flows of up to 4 steps on Essentials | Visual sequence builder, unlimited sequences |
| Transactional email | Included | Paid add-on on Standard and Premium | Included, from the same send allowance |
| Channels | Email, push, in-app, SMS, WhatsApp | Email, with SMS as an add-on | |
| Free option | No free plan; up to twelve months free for eligible startups that raised under $10 million | Free under 250 contacts; 14-day trial on Essentials and Standard | No free plan; 7-day trial, card required |
Customer.io pricing
Customer.io's Essentials plan starts at $100 per month, billed monthly, for 5,000 profiles. A profile is a person or an object, such as an account or an order. Essentials includes 1,000,000 emails a month, the visual workflow builder, transactional email, two object types, and email and community support.
Premium starts at $1,000 per month billed yearly, with custom profile and email volumes, ten object types and premium support. Enterprise is priced on a call. Above the included volume, the pricing page lists additional profiles at $0.009 each and additional email at $0.12 per 1,000. A startup program gives up to twelve months free to eligible companies that have raised under $10 million.
Mailchimp pricing
Mailchimp prices each plan by contact band. At 2,501 to 5,000 contacts, Essentials is $75 a month, Standard is $100 and Premium is $350. At 30,001 to 40,000 contacts, Essentials is $340, Standard is $410 and Premium is $750. Standard at 5,000 contacts includes 60,000 emails a month, and accounts under 250 contacts can stay on the free plan. Mailchimp also runs introductory discounts; the figures here are the regular monthly prices.
Two details change the real cost for a SaaS. First, the contact count includes unsubscribed and non-subscribed contacts, so people who opted out of marketing keep counting toward your band until you archive them. Second, transactional email is a separate product. It is available on Standard and Premium, not on Essentials, in blocks of 25,000 emails at $20 a block. Essentials also limits automation flows to four steps, which is short for a trial sequence, so most SaaS lifecycle work lands on Standard.
SendHeron pricing
SendHeron charges on subscribed contacts, with a monthly pool of sends that marketing and transactional share. The full plan details are on the pricing page.
| Plan | Price | Subscribed contacts | Sends per month |
|---|---|---|---|
| Starter | €19 per month | up to 10,000 | 50,000 |
| Growth | €49 per month | up to 40,000 | 150,000 |
| Scale | €99 per month | up to 100,000 | 250,000 |
| Max | €179 per month | up to 200,000 | 500,000 |
Only subscribed contacts count. Unsubscribed and bounced contacts are stored free. Sequences, tags and segments are unlimited on every plan. There is no free plan: every plan starts with a 7-day trial that takes a card at checkout, runs with reduced limits of 1,000 contacts and 5,000 sends, and converts to the plan you picked unless you cancel before it ends.
The pricing math
Two list sizes, the same job on each tool: lifecycle sequences plus the transactional mail a product sends anyway, with transactional staying under 25,000 emails a month.
| Scenario | Customer.io | Mailchimp | SendHeron |
|---|---|---|---|
| 5,000 contacts, 25,000 emails a month | $100 (Essentials) | $120: Standard at $100 plus one $20 transactional block | €19 (Starter) |
| 40,000 contacts, 100,000 emails a month | about $415: $100 plus 35,000 extra profiles at $0.009, our arithmetic from their listed rate | $430: Standard at $410 plus one $20 transactional block | €49 (Growth) |
Between Customer.io and Mailchimp the totals land within $20 of each other at both sizes, so pick on fit, not on price. Two things the table hides. Mailchimp's band counts unsubscribed contacts, so a SaaS that has been emailing for a few years can sit a band higher than its active list suggests. And below 250 contacts Mailchimp is free, which neither Customer.io nor SendHeron matches. If you have a few hundred users, that is the honest answer.
Feature comparison
Sequences and automation
Customer.io builds workflows in a visual editor around the people and objects your product sends it, so a branch can depend on an account's plan as easily as on a person's last login. Mailchimp's automation is built around the audience you collect: Standard and Premium allow up to 200 flows, and Essentials stops at four steps per flow. SendHeron builds sequences visually from the tags and events your app sets, and its AI setup reads your website and drafts the whole suite for you to approve: welcome, trial, win-back and cancel-save.
Transactional email
Customer.io includes transactional email on every plan. Mailchimp sells it as a separate product on top of Standard or Premium, at $20 per 25,000 emails. SendHeron includes it, and the same templates serve receipts, password resets and lifecycle mail from one send allowance. Transactional mail keeps flowing even when that allowance is spent, up to 10% over the pool.
Channels beyond email
Customer.io covers push and in-app messages, SMS on custom pricing, WhatsApp and webhooks, with mobile SDKs included. Mailchimp offers SMS as an add-on. SendHeron is email only. If your lifecycle needs a push notification or a text message, that settles it in Customer.io's favour.
What counts as a contact
This line moves the bill more than any feature. Customer.io counts profiles, which include objects as well as people. Mailchimp counts subscribed, unsubscribed and non-subscribed contacts; cleaned, pending and archived contacts do not count. SendHeron counts only subscribed contacts and stores unsubscribed and bounced ones free.
Developer surface
Customer.io has APIs, webhooks and mobile SDKs for product teams that send their own data. SendHeron has a REST API with scoped tokens and a Node SDK, and its documentation is written so an AI coding agent can wire it up.
Who should use what
Choose Customer.io if
- Your lifecycle runs across push, in-app or SMS as well as email
- You model accounts, orders or other objects and want to branch on them
- You have raised under $10 million and qualify for up to twelve free months through their startup program
Choose Mailchimp if
- You have fewer than 250 contacts and want to pay nothing for now
- Most of your email is newsletters and campaigns to an audience rather than messages triggered by product events
- You want campaign tools, templates and audience management in one product rather than a lifecycle system
Choose SendHeron if
- You run a SaaS with 2,000 to 200,000 contacts and want the lowest price per contact of the three
- You would rather approve a drafted lifecycle suite than build one from a blank canvas
- You want one API and one send allowance for transactional and marketing mail
We also compare SendHeron directly in SendHeron vs Customer.io, list other options in Customer.io alternatives, and look at three other common pairings in Loops vs Customer.io, Customer.io vs Intercom and Customer.io vs HubSpot. If you are choosing an email API for transactional mail instead, see Resend vs SendGrid, Postmark vs Resend and Mailgun vs Resend.
Frequently asked questions
Is Customer.io more expensive than Mailchimp?
Not at the sizes most SaaS products are. At 5,000 contacts both start at $100 a month, and at 40,000 contacts they are about $415 and $410. Mailchimp adds $20 per 25,000 transactional emails on top, where Customer.io includes them.
Does Mailchimp count unsubscribed contacts?
Yes. Mailchimp's own help page lists unsubscribed and non-subscribed contacts as counting toward the monthly contact limit, while cleaned, pending and archived contacts do not. Archiving people who opted out keeps your band down.
Does Mailchimp include transactional email?
Not in its marketing plans. Transactional email is a separate add-on for Standard and Premium, sold in blocks of 25,000 emails at $20 a block. Essentials is not eligible.
Does Customer.io have a free plan?
No. A startup program gives up to twelve months free to eligible companies that have raised under $10 million, and paid plans start at $100 a month.
Can I move from Customer.io or Mailchimp to SendHeron?
Contacts and tags come over through the REST API. Sequences are rebuilt rather than imported, and the AI setup drafts the first version of each one from your website, so you edit instead of starting empty.
Start with the one that fits
If you send push, in-app or SMS alongside email, start with Customer.io. If you mostly send newsletters and campaigns, or have fewer than 250 contacts, start with Mailchimp. If you run a SaaS, want lifecycle and transactional email on one bill, and would rather approve a drafted suite than build one, start a 7-day trial of SendHeron. It takes a card; cancel before it ends and you will not be charged.