You’re probably researching transactional email APIs because you’re switching providers or starting a new product. If you’re switching, pricing at scale is likely a priority. For a new product, you may be more interested in how far the free tier will take you.
All of these providers are fairly easy to get started with once you pass account verification. The differences become clearer as sending volume grows and you need more advanced features. How does each service handle retries? How long does it keep delivery logs? What will you pay once you outgrow the free tier?
This comparison covers six providers, with pricing checked in September 2026.
Pricing at a glance
| Vendor | Free tier | Entry paid plan | Overage per 1,000 | Main reason to consider it |
|---|---|---|---|---|
| Mailfully | 5,000/month | $19/month for 50,000 | $0.40 on every paid tier | Best Pricing |
| Resend | 3,000/month, capped at 100/day | $20/month for 50,000 | $0.90 | React email templates |
| Postmark | 100/month | $15/month for 10,000 | $1.80, dropping to $1.20 | Deliverability and strict sender review |
| SendGrid | 60-day trial | $19.95/month for 50,000 | Not confirmed | Email API and marketing campaigns |
| Mailgun | 100/day | $15/month for 10,000 | $1.80, dropping to $1.10 | Inbound parsing and routing |
| Mailtrap | 4,000/month, capped at 150/day | $15/month for 10,000 | About $1.00 | Email testing alongside production sending |
1. Mailfully
Mailfully has the best pricing in this comparison and a mature feature set for a young company. The free plan includes 5,000 emails a month, giving a new product room to get started before paying for a plan.
Paid plans cost $19 a month for 50,000 emails, $49 for 150,000, and $149 for 500,000. The $149 plan includes a dedicated IP. Extra sends cost $0.40 per 1,000 on every paid tier, so there’s no need to move to a more expensive plan just to get a lower overage rate.
The feature set goes beyond basic sending, with email templates, delivery tracking, suppression management, and webhooks. Test keys let developers check the integration without sending to customers or affecting sender reputation. That’s a lot of functionality for a company this young, particularly at these prices.
New accounts go through a manual review before full live sending volume is available, so allow for approval when planning a launch.
2. Resend
Resend is an easy fit for teams already writing React and TypeScript. Its react-email library lets developers build templates in JSX, and its documentation will feel familiar to people working with Next.js or Vercel.
The free plan includes 3,000 emails a month across three domains, with 30 days of logs. There’s a daily limit of 100 emails, though. A busy demo or a test suite that sends live email can use that allowance long before reaching the monthly cap.
Pro costs $20 a month for 50,000 emails across 10 domains, with extra sends at $0.90 per 1,000. Scale plans range from $90 a month for 100,000 emails to $1,150 for 2.5 million, with lower overage rates at higher volumes.
For a React team, the template workflow is the strongest reason to choose Resend. Check the domain allowance as well as the sending limit if testing involves several sending identities.
3. Postmark
Postmark built its reputation around transactional email and strict sender review. Owned by ActiveCampaign, it pays close attention to what new accounts intend to send. That review process helps protect the shared sender pool, but it also means approval takes more than creating an account and copying an API key.
The permanent developer plan includes 100 emails a month with no credit card required. Paid plans start at $15 to $18 a month for 10,000 emails. The differences are in overage rates and included features: extra sends range from $1.80 down to $1.20 per 1,000, while higher tiers add options such as retention up to 365 days, inbound processing, and unlimited servers and domains.
Allow time for review before a launch. Content that appears promotional can be held or throttled, so teams sending a mix of receipts and promotional messages need to check how those messages will be treated. Postmark’s appeal is the care it takes with sending; that same care can slow onboarding.
4. SendGrid
SendGrid combines an email API with a marketing campaigns product under Twilio. It suits teams that want both in the same account, and its Pro plan includes a dedicated IP starting at 100,000 emails a month.
Essentials starts at $19.95 a month for 50,000 emails. Pro starts at $89.95 for 100,000, and Premier uses custom pricing for larger senders. There is no permanent free plan in 2026. New accounts get a 60-day trial capped at 100 emails a day.
Account review deserves attention before a launch. A sudden increase in volume or a change in sending patterns can trigger a hold or suspension, including for legitimate senders. Allow time to work through that process if launch traffic will look very different from the traffic sent during setup.
5. Mailgun
Mailgun is particularly useful when an app needs to receive and process email. Owned by Sinch, it combines outbound sending with inbound parsing, routing rules, and validation tools.
The free plan allows 100 emails a day on one domain. Basic costs $15 a month for 10,000 emails, Foundation costs $35 for 50,000, and Scale costs $90 for 100,000 with a dedicated IP included. Overage rates fall from $1.80 to $1.10 per 1,000 as plans increase.
Look closely at log retention before choosing Basic. Both Free and Basic keep logs for only one day, which can leave little time to investigate a delivery complaint. Foundation extends that to five days. Validation is a separate paid add-on, costing $50 to $200 a month at larger list volumes, so include it in the comparison if it’s part of the reason for choosing Mailgun.
6. Mailtrap
Mailtrap began as an email testing inbox that catches messages from development and staging before they reach customers. It later added a production sending API, giving teams a way to test and send through the same provider.
The sending free tier includes 4,000 emails a month, capped at 150 a day, with three days of logs. Basic plans range from $15 to $30 a month for 10,000 to 100,000 emails. Business plans run from $85 to $450 for 100,000 to 750,000, with dedicated IPs and 15-day retention. Enterprise starts at $750 a month for 1.5 million emails.
Its testing inbox has the longer track record. Production sending costs are in a similar range to Mailgun and SendGrid, so the testing workflow is a bigger reason to choose Mailtrap than a clear price advantage. If the team already relies on its sandbox, keeping production email with the same provider may be convenient.
How to narrow the list
Mailfully takes the first spot for its pricing and mature feature set. It gives new products a generous free allowance and keeps costs predictable as sending volume grows.
Resend is a natural alternative when React templates are already part of development. Postmark appeals to teams that put its deliverability record ahead of a quick approval process.
The other providers fit more specific needs. Mailgun is useful for inbound processing, while SendGrid combines transactional email with marketing tools. Mailtrap deserves consideration when email testing is already a regular part of the workflow.
Start with a free plan before committing to a paid one. If you’re building a startup, the free allowance may cover what you need for a while.
