Customer.io is a marketing automation platform: profiles, segments, journeys and data pipelines, priced by the people in your database, with transactional email as a feature of the App API. Notix is an email API priced by what you send: 5,000 emails a month free, then 50,000 for $15, with templates, idempotency keys, one-time codes by email or SMS, an SMTP relay and signed webhooks. Teams whose marketing runs on behavioural segments should stay; teams that bought Customer.io to send receipts and resets are paying for a database they do not use.
Customer.io's pricing page sizes Essentials at 5,000 profiles and 1 million emails a month and does not print the price; the number that grows your bill is people in the database, whether or not you mail them. A transactional workload pays for profiles it never segments.
The transactional call identifies the person as well as the address. That fits a lifecycle platform and gets in the way of a receipt to a guest checkout or a code to a first-time number.
Customer.io offers a free year to startups that have raised under $10M and otherwise no free tier. It does not generate or check one-time codes, has no pre-send deliverability check, and its custom SMTP is for its own sending on some plans, not a relay your application talks to.
Every Customer.io figure was read from Customer.io's own pricing page and API docs on 2026-09-13; the date sits under the table. Where a row says a price or fact is not stated, the pages did not state it and this page does not guess.
| Criterion | Customer.io | Notix |
|---|---|---|
| Free tier | No free plan; a free year for startups that have raised under $10M | 5,000 emails a month, 200 a day, no card, no end date |
| Entry paid plan | Essentials: price not shown on the pricing page | Pro $15 a month |
| Included on that plan | Essentials: 5,000 profiles and 1 million emails a month; extra emails $0.12 per 1,000 | 50,000 emails, usage past that metered on the same invoice |
| SMTP relay | Custom SMTP on some plans; transactional sends go through the API | Yes, on every plan |
| SDKs | Mobile SDKs for iOS, Android, React Native, Expo and Flutter; server languages not listed | TypeScript, Python, Go, PHP |
| Webhooks | Yes, reporting webhooks | Yes, signed, for email, contact and domain events |
| OTP / verification API | No | Yes, email and SMS codes |
| Deliverability check before sending | No | Yes, a pre-send check API |
| Billing outside USD | USD | USD by card; naira and shillings from a prepaid wallet |
| SLA | Not stated on the pricing page | 99.9% on Pro, credits on the pricing page |
| Prices and limits read from the vendors' own pages: customer.io on 2026-09-13. Notix figures are from its own pricing page. | ||
Everything that is not sending. Segmentation on attributes and events, journeys across email, push, SMS and in-app, data pipelines, a million emails a month inside Essentials, mobile SDKs for five platforms, and a free year for early startups. If your growth team lives in segments and journeys, Customer.io is the right tool and this page is not for you.
Both send a transactional email from an API call with a template and data, both return an id, both deliver reporting events by webhook, and both bill in US dollars by card for teams outside Africa. Whether Customer.io's webhooks are signed, and what it charges, its pages do not say, so those rows are left as read.
5,000 emails a month and 200 a day, no card, no funding round required.
A price on the page, per email sent, with usage past the allowance metered on the same invoice; the pricing page has the per-unit rate.
The recipient is a field in the call. Guest checkouts and first-time numbers need nothing created first.
One call sends a code by email or SMS, one call checks it. Expiry, attempts, rate limits and risk scoring are handled server-side. See OTP email.
smtp.usenotix.dev for anything that already speaks SMTP, and events signed with HMAC-SHA256 that the SDKs verify in one call.
A prepaid wallet in NGN or KES, topped up locally. Pro is charged from the balance each month; no dollar card needed.
The App API call becomes a Notix send with the same variables and no identifiers. Keep Customer.io for the segments and journeys if that is what it is for; move the receipts and codes.
// Customer.io transactional send over its App API
const response = await fetch("https://api.customer.io/v1/send/email", {
method: "POST",
headers: {
Authorization: `Bearer ${process.env.CUSTOMERIO_APP_API_KEY}`,
"Content-Type": "application/json",
},
body: JSON.stringify({
transactional_message_id: "receipt",
to: "customer@example.com",
identifiers: { email: "customer@example.com" },
message_data: { orderId: "48213" },
}),
});
import { Notix } from "notix-js";
const notix = new Notix(process.env.NOTIX_API_KEY);
const { data, error } = await notix.emails.send(
{
from: "receipts@acme.com",
to: "customer@example.com",
templateId: "tpl_receipt_v4",
variables: { orderId: "48213" },
},
{ idempotencyKey: "order-48213-receipt" },
);
// No profile needs to exist first: the recipient is just an address.
# Customer.io offers custom SMTP on some plans for its own sending;
# Notix is the relay your app talks to.
SMTP_HOST=smtp.usenotix.dev
SMTP_PORT=465 # or 587 for STARTTLS
SMTP_USER=notix
SMTP_PASS=<your Notix API key>
Add the SPF, DKIM and DMARC records Notix gives you. They sit beside Customer.io's records, so both can send while you switch. The quickstart walks through it.
Recreate each transactional message in the Notix editor with the same variable names, then replace the App API call with notix-js and an idempotency key named after the order or event. The address is the recipient; drop the identifiers.
Export bounced and complained addresses from Customer.io, save them as a .csv or .txt with one address per line, and upload the file under Suppressions in the dashboard before the first send.
| Emails a month | Customer.io | Notix |
|---|---|---|
| 3,000 | Essentials; price not shown on the pricing page (no free plan outside the startup year) | Free, $0 |
| 50,000 | Essentials; price not shown, 1 million emails included | Pro, $15 |
| 100,000 | Essentials; price not shown, 1 million emails included | Pro, $15 plus the 50,000 above the allowance, metered on the same invoice |
Customer.io's pricing page sizes Essentials by profiles and includes a million emails but does not print a price, so the comparison at any volume is a quote against a listed number. Notix overage is at the per-unit rate on the pricing page. Customer.io facts read on 2026-09-13.
Teams in Nigeria and Kenya fund a prepaid wallet in naira or shillings through local payment methods and Pro is charged from that balance each month, so nobody needs a dollar card that clears international charges. SMS to Nigerian and Kenyan numbers is prepaid from the same wallet. The local price per email is on the pricing page when you open it from either country.
A free plan with no card, and Pro at $15 a month for 50,000 emails. Only sent volume is metered.
AlternativesA Courier alternative when you want the email itself, not an orchestration layer: templates, batch sends, webhooks and OTP in one email API.
AlternativesA Loops alternative for teams who need a transactional API with webhooks, OTP codes and SMTP, not only a marketing tool for SaaS.
ProductOTPs, receipts and alerts with idempotency keys, a deliverability pre-check and a shared suppression list.
Use casesA welcome sent on sign-up, or a short sequence through a journey, with double opt-in built in for imported lists.
AlternativesHonest switch pages for the email APIs people move away from, with the vendor's own numbers and read dates.
5,000 emails a month on Free. When you outgrow it, Pro is $15 for 50,000, payable by card or from a naira or shilling wallet.