# Best email API for startups in 2026: what's really free? > Email, SMS and WhatsApp priced at 0, 1,000 and 10,000 users: from $0 to over $200 a month depending on the stack. Sourced prices, November 2026. Source: https://unlimitedmessaging.app/articles/messaging-api-indie-hackers Builder guide # The indie hacker messaging stack: _what email, SMS and WhatsApp really cost at 0, 1k and 10k users_ Every SaaS ends up sending welcome emails, login codes and notifications. Free tiers look generous until launch day. Here is the bill for email, SMS and WhatsApp at three stages, with Resend, Postmark, SendGrid, Twilio, Brevo and Unlimited Messaging, prices read on the vendors' pages on November 9, 2026, and the signals that tell you when to switch. [Start free](https://app.unlimitedmessaging.app)[View pricing](https://unlimitedmessaging.app/pricing) The short answer ## Which messaging API is really free for a startup? For email alone, Resend's free tier (3,000 a month, 100 a day) is the best developer experience until launch. For SMS and WhatsApp, no carrier-route API is free: Twilio bills every message. Unlimited Messaging is the only option here that stays free on all three channels, because it sends from your own mailbox, WhatsApp number and Android phone. We priced a simple SaaS: each active user gets 3 transactional emails a month (welcome, receipt, reset), 1 SMS code and 1 WhatsApp notification. At 1,000 users that is 3,000 emails, 1,000 SMS and 1,000 WhatsApp messages a month; at 10,000 users, ten times more. US numbers for SMS, because they are the most common benchmark. The result: at 10,000 users, a classic stack of Resend Pro, Twilio SMS and Twilio WhatsApp costs about $220 to $240 a month before 10DLC registration fees, and most of it is per-message SMS. The same traffic from your own accounts costs nothing per message, but runs into hard limits: 500 emails a day on Gmail, 30 SMS per 30 minutes on Android. So the honest answer depends on the stage. Free from your own accounts while you test and grow, then a paid sending service for the one channel that outgrows your mailbox or phone, not for all three at once. Deep dives: [Twilio alternative](https://unlimitedmessaging.app/articles/twilio-alternative), [Brevo alternative](https://unlimitedmessaging.app/articles/brevo-alternative) and [the cheapest SMS API in 2026](https://unlimitedmessaging.app/articles/cheap-sms-api). ![Illustration: a rising bar chart, with the headline “What's really free?”.](https://unlimitedmessaging.app/_next/image?url=%2Fassets%2Farticles%2Fcovers%2Fmessaging-api-indie-hackers-en.png&w=3840&q=75) Definition Free tier vs free trial A free trial ends after a set time (SendGrid: 60 days). A free tier stays free but caps volume (Resend: 100 emails a day). A free plan on your own accounts has no message cap, only your provider's limits and, at Unlimited Messaging, a short footer. Also searched as: cheapest notification API, free messaging API for startups, best email API for startups. [Source: Resend pricing↗](https://resend.com/pricing) The bill ## How much do email, SMS and WhatsApp cost at 0, 1,000 and 10,000 users? Monthly cost of each provider for its own channel, with 3 emails, 1 SMS and 1 WhatsApp message per user per month. Taxes and phone numbers excluded. transactional emails per user per month 3transactional emails per user per month SMS code per user per month (US) 1SMS code per user per month (US) WhatsApp notification per user per month 1WhatsApp notification per user per month __How much do email, SMS and WhatsApp cost at 0, 1,000 and 10,000 users?__ | 0 users (building) | 1,000 users | 10,000 users | | | -------------------------- | ------------------------------------------- | ------------------------------------------------------- | ----------------------------------------------------------------------------------- | | Resend (email) | $0: 3,000 emails a month, 100 a day | $0 on paper; the 100-a-day cap pushes you to Pro at $20 | Pro: $20 for 50,000 emails | | Postmark (email) | $0: 100 emails a month | Basic: $15 for 10,000 emails | About $51: Basic $15 plus 20,000 extra at $1.80 per 1,000 | | SendGrid (email) | $0 for 60 days, 100 a day | Essentials from $19.95 | Essentials from $19.95 | | Twilio (SMS, US) | Pay per message, 10DLC registration first | About $12 to $13 | About $118 to $133 | | Twilio (WhatsApp) | $0.005 + Meta's fee per template | From about $8.40 | From about $84 | | Brevo (email + SMS) | $0: 300 emails a day; SMS bought as credits | Email $0; SMS credits extra (100 to France from €4.50) | Paid Starter tier for 30,000 emails (from $9 for 5,000) plus SMS credits | | Unlimited Messaging Free | €0 on all three channels, short footer | €0: 3,000 emails fit Gmail, SMS on your carrier plan | €0, but 1,000 emails a day is over Gmail's 500: use Workspace or your domain's SMTP | | Unlimited Messaging Medium | €19 a month, no footer, webhooks | €19 a month | €19 a month, same mailbox and phone limits | Prices read on November 9, 2026 on resend.com/pricing, postmarkapp.com/pricing, Twilio's SendGrid, SMS and WhatsApp pricing pages and brevo.com. Twilio SMS = $0.0083 per segment plus a $0.0035 to $0.005 carrier fee, one segment per code. Twilio WhatsApp = $0.005 plus Meta's fee, from $0.0034 depending on the country. Brevo's Starter price grows with email volume; check the exact tier on its page. Unlimited Messaging SMS count against your own carrier plan. At 10,000 users ## What does the whole stack cost per month? Email, SMS and WhatsApp added up for the same 10,000 users. Resend Pro for email $20Resend Pro for email Twilio SMS, before 10DLC fees \~$125Twilio SMS, before 10DLC fees Twilio WhatsApp, Meta's fee included $84+Twilio WhatsApp, Meta's fee included Unlimited Messaging Medium, all three channels €19Unlimited Messaging Medium, all three channels Reading the numbers ### SMS is what makes the bill grow Email APIs stay cheap at this scale: $20 a month at Resend. Per-message SMS is what climbs, then WhatsApp templates. Sending those two from your own phone and number removes the variable part; email can stay on Resend once it outgrows your mailbox. The fine print ## What does "free" really mean on each platform? Five kinds of free, and what each one costs you later. 1. 01 ### Free trial (SendGrid) 100 emails a day for 60 days, then a paid plan from $19.95 a month. Good to test, not a plan to launch on. 2. 02 ### Capped free tier (Resend, Postmark, Brevo) Free forever within a quota: 100 emails a day at Resend, 100 a month at Postmark, 300 a day at Brevo. One busy launch day goes over. 3. 03 ### Pay as you go (Twilio) No monthly fee, but every SMS and WhatsApp message is billed, and US SMS needs A2P 10DLC registration before the first text. 4. 04 ### Free plan on your own accounts (Unlimited Messaging) No message cap and no per-message fee on email, WhatsApp and SMS, with a short footer on each message. The limits are your mailbox provider's, your phone's and WhatsApp's fair use. 5. 05 ### Self-hosted (open source) Free software, paid server and your own time: SMTP relays, WhatsApp libraries or SMS gateways you run and keep alive yourself. The roadmap ## When should you switch to a paid messaging API? A stack by stage. Switch one channel at a time, when its own limit shows up. 1. 01 ### Building (0 users) One free API for the three channels: connect Gmail, your WhatsApp number and an Android phone, and test every flow without a card. 2. 02 ### First 1,000 users Still free. Take Medium at €19 a month when you want the footer gone or webhooks for replies and delivery statuses. 3. 03 ### Around 10,000 users Over 500 emails a day, move receipts to Google Workspace, your domain's SMTP or Resend Pro. Keep WhatsApp and SMS on your own number. 4. 04 ### Bursts, compliance, cold outreach OTP spikes of hundreds a minute, regulated industries or messages to strangers at scale: use Twilio Verify, official WhatsApp templates and a marketing email service. The code ## What does one call for three channels look like? One request sends one message per channel and groups them under a shared dispatchId. Drop the channels you do not need. POST /messageTypeScript ``` const res = await fetch('https://api.unlimitedmessaging.app/message', { method: 'POST', headers: { Authorization: `Bearer ${process.env.UM_API_KEY}`, 'Content-Type': 'application/json', }, body: JSON.stringify({ "to": { "email": "user@example.com", "phone": "+447700900123" }, "subject": "Your Acme receipt", "text": "Payment received, thank you! Your receipt is in your account.", "channels": [ { "channel": "EMAIL" }, { "channel": "WHATSAPP" }, { "channel": "SMS" } ] }), }); ``` TypeScript with fetch. The same body works from Python, curl, n8n or the SDKs. Prompt for Lovable, Bolt, v0, Cursor or Claude CodePrompt ``` Add Unlimited Messaging as the messaging layer of this app. Install @unlimited-messaging/sdk or use fetch, and read UM_API_KEY from the server environment only. Create a server-side notify(user, event) helper that calls POST https://api.unlimitedmessaging.app/message with Authorization: Bearer UM_API_KEY. Body: to: { email: user.email, phone: user.phone } (E.164), subject, text, channels: one entry per channel the user opted into among { channel: 'EMAIL' }, { channel: 'WHATSAPP' }, { channel: 'SMS' }. Use it for: welcome on signup (email + WhatsApp), payment receipt (email), important alert (WhatsApp, SMS if no WhatsApp). Add a notification preferences screen with the three channels. Log failures and never block the user flow. Reference: https://unlimitedmessaging.app/llms-full.txt ``` Paste it into your AI coding tool. Create the API key in the Unlimited Messaging app first and store it as a server-side secret. FAQ ## Questions about the indie hacker messaging stack For email only, Resend has the best developer experience and $20 a month covers 50,000 emails. If you also need SMS and WhatsApp and want to stay free while you grow, Unlimited Messaging sends all three from your own accounts in one API call. Sending from accounts you already own: no per-message fee with Unlimited Messaging, free plan included, Medium at €19 a month. Among per-message APIs, email is cheap (Resend Pro: $20 for 50,000), US SMS is about $0.012 to $0.013 at Twilio with carrier fees. Not on carrier routes or Meta's official platform, which bill per message. Unlimited Messaging's free plan covers both: WhatsApp from your linked number (unofficial, linked as a device) and SMS from your Android phone's SIM. 500 a day on a personal Gmail account and 2,000 per user on paid Google Workspace, according to Google. Past that, use your domain's own SMTP server or a sending service like Resend. Start with one to ship fast. Split later, by channel, when one hits its limit: email to Resend or Postmark past your mailbox's daily cap, OTP bursts to Twilio Verify, and keep the rest on your own accounts. It is unofficial: your number is linked as a device, like WhatsApp Web. It suits messages to people who know you at a human pace. Bulk messages to strangers get numbers banned; use Meta's official platform for that. Sources ## Sources & references To check the information in this article for yourself: 1. [01Resend pricing (Free: 3,000 emails a month, 100 a day; Pro $20 for 50,000)↗Resend](https://resend.com/pricing) 2. [02Postmark pricing (Free 100 emails a month, Basic $15 for 10,000, $1.80 per extra 1,000)↗Postmark](https://postmarkapp.com/pricing) 3. [03Email API pricing (60-day trial at 100 emails a day, Essentials from $19.95)↗Twilio SendGrid](https://www.twilio.com/en-us/pricing/email-api) 4. [04SMS pricing in the United States ($0.0083 per segment, carrier fees)↗Twilio](https://www.twilio.com/en-us/sms/pricing/us) 5. [05WhatsApp pricing ($0.005 per message plus Meta's template fee, from $0.0034)↗Twilio](https://www.twilio.com/en-us/whatsapp/pricing) 6. [06A2P 10DLC brand registration↗Twilio Docs](https://www.twilio.com/docs/trust-hub/registrations/a2p-10dlc-brand) 7. [07Brevo pricing plans (Free, Starter, Standard)↗Brevo](https://www.brevo.com/pricing/) 8. [08Bulk SMS sender (100 SMS credits in France from €4.5)↗Brevo](https://www.brevo.com/bulk-sms-sender/) 9. [09SMS and WhatsApp cost calculator (300 free emails a day)↗Brevo](https://www.brevo.com/tools/ecommerce-tools/sms-whatsapp-cost-calculator/) 10. [10Limits for sending and getting mail (500 emails a day)↗Gmail Help](https://support.google.com/mail/answer/22839) 11. [11Gmail sending limits in Google Workspace (2,000 a day per user)↗Google Workspace Admin Help](https://knowledge.workspace.google.com/admin/gmail/gmail-sending-limits-in-google-workspace) ![Ilian, senior software engineer](https://ilianazz.com/images/iliazz.png) Written by [Ilian](https://unlimitedmessaging.app/authors/ilian) · Senior Software Engineer A senior software engineer, he founds and runs several tech companies. He builds products around messaging APIs, automation and AI integration, and shares here what he learns while building. [View LinkedIn profile↗](https://www.linkedin.com/in/ilianAzz/)Updated November 9, 2026 ![](https://unlimitedmessaging.app/assets/logos/whatsapp.svg)![](https://unlimitedmessaging.app/assets/logos/email.svg)![](https://unlimitedmessaging.app/assets/logos/sms.svg) ## Ship email, SMS and WhatsApp for free. Connect your mailbox, your WhatsApp number and your Android phone, create an API key and send from your app in one call. 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