Use case · Transactional email

Transactional email for a startup: what it costs from 3,000 to 300,000 emails a month

Sign-up confirmations, receipts and password resets. Here is what each email API in the Stackcut catalog costs at your volume, which free plans are really free, and the one question to ask your agent.

By Stackcut · Published · Catalog of 2026-09-25 · Vendor prices checked 2026-09-25

Modeled, not measured. Savings use public prices and planning assumptions: the bill you stop paying, minus the new tool, your upkeep time and your setup time at $50/hour, over the first 12 months. Results marked Tested by Stackcut are Stackcut's own test, not a customer. Every price links the page it came from.

The short answer

  • Under 3,000 a month and 100 a day: Resend's free plan, which doesn't expire. resend.com
  • At 50,000 a month: $5/mo on Amazon SES, $19.95/mo on SendGrid, $20/mo on Resend. aws.amazon.com
  • Amazon SES is the cheapest per email in the catalog at $0.10 per 1,000 with no minimum, but new AWS accounts get credits, not an always-free SES allowance. aws.amazon.com
  • SendGrid's free option is a 60-day trial, and Postmark's free Developer plan is 100 emails a month. twilio.com

The economics

The cheapest published plan for each provider at each volume, including published overage, from each vendor's pricing page.

Monthly cost by volume

Cheapest published plan plus published overage, billed monthly; not a quote. Free plans with a daily cap assume sends spread over 30 days. Each price links the vendor's pricing page.
Emails a month3,00010,00050,000100,000300,000
Resend$0Free, 100/day cap$20Pro$20Pro$35Pro 100k$215Pro 100k, plus overage
SendGrid (Twilio)$19.95Essentials$19.95Essentials$19.95Essentials$34.95Essentials 100k$214.95Essentials 100k, plus overage
Postmark$15Basic$15Basic$66Platform, plus overage$126Platform, plus overage$366Platform, plus overage
Mailgun$0Free, 100/day cap$15Basic$35Foundation$90Scale$310Scale, plus overage
Amazon SESattachments extra$0.30Pay as you go$1Pay as you go$5Pay as you go$10Pay as you go$30Pay as you go
  • Postmark's page shows only its 10,000-email step, so above that the catalog prices extra emails at the published overage; check its slider for volume tiers. postmarkapp.com

What the free tiers really are

OptionKindWhat the free tier includes
ResendFree3,000 emails/mo, 100 emails/day, 3 domains, 30-day data retention; no pay-as-you-go on Free
MailgunFree100 emails/day, 1 custom sending domain, 1 user, 1-day log retention
PostmarkFreeDeveloper plan: 100 emails/month, never expires; no overages allowed
SendGrid (Twilio)Trial onlyFree trial: 100 emails/day and 100 contacts for 60 days; limits can't be exceeded
Amazon SESOne-time creditNo always-free SES allowance: new AWS accounts get $100 in AWS Free Tier credits at sign-up (up to $200 with activities), usable for 6 months; the Free-plan account closes after 6 months or when credits run out

Pick by situation

A real workflow: ask your agent

  • Ask your agent to price the job at your real volume. choose_stack returns, per provider, the cheapest published tier that covers your number, with a link to the pricing page, and asks for any number it doesn't have. stackcut.io
choose_stack({"project": "B2B SaaS app", "needs": [
  {"job": "email_transactional",
   "volume": {"amount": 40000, "unit": "emails_per_month"}}]})
  • A plan counts as a fit only when its published limit covers your number; trials and one-time credits never count as free. stackcut.io

Fit

A good fit if

  • You send transactional email from your app through an API or SMTP. recipe
  • You know roughly how many emails you send a month, or can read it off your provider's dashboard. recipe

Look elsewhere if

  • You send newsletters to a list: that's email marketing, priced by subscribers. See the newsletter use case. recipe
  • Inbound email, templates or broadcasts are core to your product: check each plan's extras, not only the send price. recipe

Questions

Is Resend's free plan enough for a startup?

Until you pass 3,000 emails a month or 100 in a day. Free has no pay-as-you-go, so plan the upgrade before launch day. resend.com

Which free plans are really free?

Resend's is an ongoing free plan: 3,000 emails/mo, 100 emails/day, 3 domains, 30-day data retention; no pay-as-you-go on Free. resend.com

Mailgun's free plan allows 100 emails a day. mailgun.com

Postmark's Developer plan is 100 emails a month. postmarkapp.com

SendGrid's is a 60-day trial. twilio.com

Amazon SES gives new AWS accounts credits instead of a free allowance. aws.amazon.com

What does SES cost at 300,000 emails a month?

$30/mo, before attachments, at the a la carte rate of $0.10 per 1,000. aws.amazon.com

How do I switch providers without losing mail?

Add the new provider's DNS records for your sending domain first, switch the API key in your app, watch a day of sends, then cancel the old plan. recipe

Next steps

Check your own stack

Get your free stack audit

Stackcut finds every software subscription in your inbox and shows what to cancel, what to pay per use, and what AI can replace, with a spec and a cost for each. Your stack audit is free and takes about 2 minutes.

Get my free stack audit

Or ask your agent

Connect the Stackcut MCP server (https://stackcut.io/mcp, no API key) and ask: “We send about 40,000 transactional emails a month. What's the cheapest provider that fits?”

choose_stack({"project": "B2B SaaS app", "needs": [
  {"job": "email_transactional",
   "volume": {"amount": 40000, "unit": "emails_per_month"}}]})