Starter
For your first email program.
$16USD / month
$192 billed yearly.
20,000 emails / month
Choose Starter- 5 brands · 3 seats
- 5 custom sending domains
- 500 email verifications/month
- $1.50 / 1,000 extra emails
Nitrosend is the best email API for developers who run email from AI agents, with the top score of 83.75 out of 100 across the eight reviewed here. It is the only one your AI assistant, whether Claude, ChatGPT, Cursor or Codex, can sign up to and send from without anyone opening a dashboard, and it scores 9 out of 10 on working from your AI assistant, the heaviest test on the page. To send email from an AI agent with Nitrosend, add its MCP server at api.nitrosend.com/mcp in Claude, ChatGPT, Cursor or Codex and sign in once with OAuth; a script or headless agent can instead sign up, mint a key and send over plain HTTP. Its typed Node SDK, its CLI and its MCP server all reach the whole platform, so your receipts, newsletters and automated flows run on one key and one bill. It costs $20 a month for 20,000 emails. Resend comes next at 77.5, then Loops at 73.
The ranking
Rank 1Nitrosend
83.75 out of 100Total
- Priced by
- Emails sent
- Free plan
- 5,000 emails, then 500 a month
- Entry plan
- $20 a month, 20,000 emails
- Works from your AI assistant9 out of 10Official MCP server, account signup over the API and a ready-made sender, so an agent sends with no dashboard (docs).
- Receipts and newsletters on one plan9 out of 10Receipts, campaigns and flows share one plan, one API and one allowance, on separate streams (pricing).
- Emails in your brand, no designer9 out of 10Brand Kit reads your site for logo, colors, fonts and voice, and every drafted email uses it (docs).
- Free plan7 out of 105,000 emails up front, then 500 every month, no card and no expiry (pricing).
- Price8.5 out of 10$20 a month for 20,000 emails on Starter and $650 for a million emails on Scale including overage, with unlimited contacts on every plan (pricing).
- Developer tools10 out of 10REST API with an OpenAPI spec, a typed TypeScript SDK, a CLI, an MCP server, signed event webhooks, idempotent sends and test sends (docs).
- Track record and support4 out of 10A young product from a small team. Dedicated IPs available as a provisioned add-on on Scale or Enterprise, a 99.9% SLA only on Enterprise (pricing).
Nitrosend
Ask your agent for the next campaign
Connect Nitrosend to Claude, ChatGPT, Cursor or Codex, point Brand Kit at your site, and describe the email. Contacts are unlimited on every plan.
Free: 5,000 emails to start, then 500 a month. No credit card.
Start free
Rank 2Resend
77.5 out of 100Total
- Priced by
- Emails sent, plus contacts for marketing
- Free plan
- 3,000 emails a month, 100 a day
- Entry plan
- $20 a month, 50,000 emails
- Works from your AI assistant8 out of 10Hosted MCP server with OAuth, plus agent plugins and a CLI, but a person creates the account and verifies a domain (docs).
- Receipts and newsletters on one plan7 out of 10Broadcasts and automations share the account and API, but marketing is a second plan priced by contacts (pricing).
- Emails in your brand, no designer6 out of 10An AI writer in the editor with URL and brand analysis listed, and React Email for coded templates (pricing).
- Free plan8 out of 103,000 emails a month, up to 100 a day, on a free plan that does not expire (pricing).
- Price9 out of 10$20 a month for 20,000 emails on Pro, the same as Nitrosend, but $650 for a million on Scale (pricing).
- Developer tools9 out of 10Official SDKs, an SMTP relay, webhooks, inbound email, React Email and a CLI on every plan (pricing).
- Track record and support6 out of 10Newer than the incumbents, with SOC 2 Type II, dedicated IPs on Scale and a 99.99% SLA on Enterprise (pricing).
Rank 3Loops
73 out of 100Total
- Priced by
- Subscribed contacts, sends unlimited
- Free plan
- 1,000 contacts, 4,000 sends a month
- Entry plan
- $49 a month, up to 5,000 contacts
- Works from your AI assistant8 out of 10Hosted MCP server at mcp.loops.so, a ChatGPT plugin, a CLI and agent skills, but a person signs in and each transactional email is a published template (docs).
- Receipts and newsletters on one plan9 out of 10Campaigns, workflows and transactional email on every plan, through one API or SMTP, with unlimited sends on paid plans (pricing).
- Emails in your brand, no designer5 out of 10Themes set fonts and styles that cascade to every email, set up by hand rather than learned from your site (docs).
- Free plan7 out of 104,000 sends in any rolling 30 days and 1,000 subscribed contacts, with a Loops footer on every email (pricing).
- Price8 out of 10$49 a month on the smallest paid plan at either volume, because Loops prices by subscribed contacts and sends are unlimited (pricing).
- Developer tools7 out of 10Official SDKs for JavaScript, Go, PHP and Ruby, an SMTP service, signed webhooks and a CLI. No inbound email (SDKs).
- Track record and support5 out of 10An SLA and dedicated support come only on the custom Enterprise plan, and no uptime figure is on the pricing page (pricing).
Rank 4MailerSend
68.5 out of 100Total
- Priced by
- Emails sent
- Free plan
- 500 emails a month, card required
- Entry plan
- $7 a month, 5,000 emails (Hobby)
- Works from your AI assistant8 out of 10Hosted MCP server connected by OAuth that sends and schedules email, sets up domains and webhooks and reads email activity, once a person has signed up (docs).
- Receipts and newsletters on one plan4 out of 10Bulk emailing through the same API, but no campaign builder, segments or automation flows (pricing).
- Emails in your brand, no designer6 out of 10Drag-and-drop, HTML and rich-text builders with ready-made templates, which you still set up in your brand (pricing).
- Free plan5 out of 10A Free plan of 500 emails a month with 100 API requests a day, and a card on file (pricing).
- Price8 out of 10$35 a month for 20,000 emails on Starter, which covers 50,000, and $600 for a million on Starter (pricing).
- Developer tools9 out of 10Seven SDKs, an OpenAPI collection, SMTP relay, webhooks, inbound routing and testing features (pricing).
- Track record and support6 out of 10A 99.5% uptime SLA on its top plans, with dedicated IPs on Enterprise above 100,000 emails a week (pricing).
Rank 5Mailgun
67.5 out of 100Total
- Priced by
- Emails sent
- Free plan
- 100 emails a day
- Entry plan
- $15 a month, 10,000 emails
- Works from your AI assistant6 out of 10Official MCP server for sends, analytics and validation, run locally with an API key. Mailgun offers no hosted version (docs).
- Receipts and newsletters on one plan4 out of 10Mailing lists and a template builder on the sending API, but no campaign builder or automation flows (pricing).
- Emails in your brand, no designer5 out of 10An email template builder and templates API, but the brand design is yours to build (pricing).
- Free plan7 out of 10A free plan of 100 emails a day, one sending domain and one inbound route (pricing).
- Price8 out of 10$33 a month for 20,000 emails on Basic with overage, and $700 for a million on Scale (pricing).
- Developer tools9 out of 10Official SDKs in six languages, SMTP relay, webhooks, inbound routes and a validation API (docs).
- Track record and support9 out of 10A long-running sending API, now part of Sinch, with dedicated IP pools, IP warm-up and an uptime SLA (pricing).
Rank 6Amazon SES
65.5 out of 100Total
- Priced by
- Emails sent
- Free plan
- None. New AWS customers get up to $200 in credits
- Entry price
- $0.10 per 1,000 emails, or $0.16 on Essentials
- Works from your AI assistant7 out of 10AWS's own managed MCP server runs SES API calls, so an agent can send and read sending data, but it connects with IAM credentials a person sets up, and new accounts start in the SES sandbox (AWS).
- Receipts and newsletters on one plan3 out of 10A sending service with contact lists and subscription management, but no campaign builder or automation flows (pricing).
- Emails in your brand, no designer2 out of 10Stored templates are HTML and text you write yourself. There is no visual editor and no brand setup (pricing).
- Free plan4 out of 10No standing free plan. New AWS customers get up to $200 in Free Tier credits that apply to SES (pricing).
- Price10 out of 10Metered at $0.16 per 1,000 on Essentials, so $3.20 for 20,000 emails and $160 for a million (pricing).
- Developer tools9 out of 10AWS SDKs in every major language, SMTP, event publishing, inbound receiving and a mailbox simulator for tests (docs).
- Track record and support9 out of 10Running at Amazon scale since 2011, with managed dedicated IPs, Virtual Deliverability Manager and tenant isolation (pricing).
Rank 7Postmark
64.5 out of 100Total
- Priced by
- Emails sent
- Free plan
- 100 emails a month, no expiry
- Entry plan
- $15 a month, 10,000 emails
- Works from your AI assistant6 out of 10Official MCP server with 24 tools, run locally with a server token a person creates first (Postmark).
- Receipts and newsletters on one plan4 out of 10Broadcast streams send bulk mail from the same account, but there is no campaign builder or flows (docs).
- Emails in your brand, no designer5 out of 10A library of ready-made transactional templates, which you still edit into your own brand (Postmark).
- Free plan4 out of 10A free Developer plan of 100 emails a month that never expires, for testing (pricing).
- Price8 out of 10$29.50 a month for 20,000 emails on Pro with overage, and $775 on Basic for the 1.5 million step (pricing).
- Developer tools9 out of 10Official libraries for Node.js and TypeScript, Python, Ruby, .NET, Java and PHP, SMTP, delivery and bounce webhooks, and inbound processing (docs).
- Track record and support9 out of 10A transactional specialist since 2010, with separate streams, managed dedicated IPs and 45-day retention (pricing).
Rank 8SendGrid
59.5 out of 100Total
- Priced by
- Emails sent (Email API)
- Free plan
- Trial: 100 a day for 60 days
- Entry plan
- $19.95 a month, 50,000 emails
- Works from your AI assistant3 out of 10No first-party SendGrid MCP server. Twilio's beta MCP server searches API docs and does not send (Twilio).
- Receipts and newsletters on one plan6 out of 10Marketing Campaigns is a separate product with its own plan, priced on contacts stored (Twilio).
- Emails in your brand, no designer5 out of 10Dynamic templates, a design editor and a Designs API, but the design is yours to build (docs).
- Free plan3 out of 10A trial, not a plan: 100 emails a day for 60 days, then pay (pricing).
- Price9 out of 10$19.95 a month for 20,000 emails on Essentials, and $799 for the Pro 1.5 million step (pricing).
- Developer tools9 out of 10SDKs in seven languages, SMTP relay, event webhooks, Inbound Parse and a sandbox mode (docs).
- Track record and support8 out of 10Sending since 2009, owned by Twilio since 2019, dedicated IPs included on Pro (pricing).
How they compare
How each one scores
Scores out of 10, September 26, 2026| What we compared | Nitrosend | Resend | Loops | MailerSend | Mailgun | SES | Postmark | SendGrid |
|---|---|---|---|---|---|---|---|---|
| Works from your AI assistant25 points | 9 out of 10 | 8 out of 10 | 8 out of 10 | 8 out of 10 | 6 out of 10 | 7 out of 10 | 6 out of 10 | 3 out of 10 |
| Receipts and newsletters on one plan15 points | 9 out of 10 | 7 out of 10 | 9 out of 10 | 4 out of 10 | 4 out of 10 | 3 out of 10 | 4 out of 10 | 6 out of 10 |
| Emails in your brand, no designer10 points | 9 out of 10 | 6 out of 10 | 5 out of 10 | 6 out of 10 | 5 out of 10 | 2 out of 10 | 5 out of 10 | 5 out of 10 |
| Free plan10 points | 7 out of 10 | 8 out of 10 | 7 out of 10 | 5 out of 10 | 7 out of 10 | 4 out of 10 | 4 out of 10 | 3 out of 10 |
| Price15 points | 8.5 out of 10 | 9 out of 10 | 8 out of 10 | 8 out of 10 | 8 out of 10 | 10 out of 10 | 8 out of 10 | 9 out of 10 |
| Developer tools15 points | 10 out of 10 | 9 out of 10 | 7 out of 10 | 9 out of 10 | 9 out of 10 | 9 out of 10 | 9 out of 10 | 9 out of 10 |
| Track record and support10 points | 4 out of 10 | 6 out of 10 | 5 out of 10 | 6 out of 10 | 9 out of 10 | 9 out of 10 | 9 out of 10 | 8 out of 10 |
| Total scoreout of 100 | 83.75 out of 100,1st | 77.5 out of 100,2nd | 73 out of 100,3rd | 68.5 out of 100,4th | 67.5 out of 100,5th | 65.5 out of 100,6th | 64.5 out of 100,7th | 59.5 out of 100,8th |
Here are the nine yes-or-no questions developers usually ask before they pick an email API. A tick means the service does it, as described on its own pages today. A dash means the answer is not a clean yes or no.
8 services, side by side
Checked September 26, 2026QuestionNitrosendResendLoopsMailerSendMailgunSESPostmarkSendGrid
NitrosendResendLoopsMailerSendMailgunSESPostmarkSendGridSend from the chatCan an agent send a transactional email without anyone opening the web app?Nitrosend: Yes.Resend: Yes.Loops: Yes.MailerSend: Yes.Mailgun: Yes.SES: Not a yes or no.Postmark: Yes.SendGrid: Not a yes or no.
| Service | Answer |
|---|---|
| Nitrosend | Yes. Yes, through the MCP server. A single transactional email sends on the call; campaigns and flows stay drafts until approved. |
| Resend | Yes. Yes, once a person has created the account and verified a sending domain. |
| Loops | Yes. Yes, a published transactional email, once a person has signed in and connected the MCP server. |
| MailerSend | Yes. Yes, once a person has signed up and authorized the MCP connection. |
| Mailgun | Yes. Yes, once a person has created the account and handed the MCP server an API key. |
| SES | Not a yes or no. Only through a sample or general AWS MCP server, with AWS credentials a person sets up. |
| Postmark | Yes. Yes, once a person has set up the account and handed the MCP server a server token. |
| SendGrid | Not a yes or no. Only by writing code against the API. Twilio's own MCP server searches the docs and does not send. |
Hosted MCP serverCan a chat app connect over the web, with no local install?Nitrosend: Yes.Resend: Yes.Loops: Yes.MailerSend: Yes.Mailgun: No.SES: No.Postmark: No.SendGrid: No.
| Service | Answer |
|---|---|
| Nitrosend | Yes. Yes. A remote server at api.nitrosend.com/mcp, with OAuth sign-in. |
| Resend | Yes. Yes. A remote server at mcp.resend.com/mcp, with OAuth sign-in. |
| Loops | Yes. Yes. mcp.loops.so, with sign-in. |
| MailerSend | Yes. Yes. Connect by URL and authorize access to the account. |
| Mailgun | No. No. Mailgun's docs say the server runs locally and no hosted version exists. |
| SES | No. No hosted SES MCP server. |
| Postmark | No. No. The official server runs locally through npx with an API token. |
| SendGrid | No. No. Every SendGrid server on the official MCP registry is community built, none hosted by Twilio. |
Sign up with no personCan an agent create the account and send a first email with no DNS work?Nitrosend: Yes.Resend: No.Loops: No.MailerSend: No.Mailgun: No.SES: No.Postmark: No.SendGrid: No.
| Service | Answer |
|---|---|
| Nitrosend | Yes. Yes. Signup is an API call, and each brand gets a ready sender on a Nitrosend subdomain. |
| Resend | No. No. Resend's own agent guide says a person must create the account. |
| Loops | No. No. A person signs in to Loops in a browser. |
| MailerSend | No. No. A person signs up, with a card even on Free, and verifies a domain. |
| Mailgun | No. No. A person signs up and verifies a sending domain first. |
| SES | No. No. A person opens the AWS account, verifies a domain and requests production access. |
| Postmark | No. No. A person signs up and confirms a sender signature or domain first. |
| SendGrid | No. No. A sender or a domain has to be verified before real sending. |
Campaigns and flows in the same planDo newsletters and automations come with the transactional plan?Nitrosend: Yes.Resend: Not a yes or no.Loops: Yes.MailerSend: No.Mailgun: No.SES: No.Postmark: Not a yes or no.SendGrid: No.
| Service | Answer |
|---|---|
| Nitrosend | Yes. Yes, on every plan including Free. |
| Resend | Not a yes or no. Broadcasts and automations are in the same account, on a separate marketing plan. |
| Loops | Yes. Yes. Campaigns, workflows and transactional on every plan. |
| MailerSend | No. No. Bulk emailing, but no campaign builder or flows. |
| Mailgun | No. No. Mailing lists and templates, but no campaign builder or flows. |
| SES | No. No. SES sends, and the campaigns and flows are yours to build. |
| Postmark | Not a yes or no. Broadcast streams handle bulk sends. There is no campaign builder or automation flows. |
| SendGrid | No. No. Marketing Campaigns is a separate plan, from $15 a month. |
Perpetual free planIs there a free plan that does not run out?Nitrosend: Yes.Resend: Yes.Loops: Yes.MailerSend: Yes.Mailgun: Yes.SES: No.Postmark: Yes.SendGrid: No.
| Service | Answer |
|---|---|
| Nitrosend | Yes. Yes. 5,000 emails up front, then 500 a month. |
| Resend | Yes. Yes. 3,000 emails a month, 100 a day. |
| Loops | Yes. Yes. 4,000 sends in any 30 days, with a Loops footer. |
| MailerSend | Yes. Yes. 500 emails a month. |
| Mailgun | Yes. Yes. 100 emails a day. |
| SES | No. No. Up to $200 in AWS credits for new customers. |
| Postmark | Yes. Yes. 100 emails a month on the Developer plan, with no expiry. |
| SendGrid | No. No. 100 emails a day for 60 days, then a paid plan. |
Brand learned from your siteDoes it pick up your logo, colors, fonts and voice without a designer?Nitrosend: Yes.Resend: Not a yes or no.Loops: No.MailerSend: No.Mailgun: No.SES: No.Postmark: No.SendGrid: No.
| Service | Answer |
|---|---|
| Nitrosend | Yes. Yes. Brand Kit scans your site, and AI Memory keeps house style. |
| Resend | Not a yes or no. Its AI features list URL and brand analysis, which its docs do not describe yet. |
| Loops | No. No. Themes are set up by hand. |
| MailerSend | No. No. Templates are built in its editors. |
| Mailgun | No. No. Templates are built in its builder or in HTML. |
| SES | No. No. Templates are HTML you write. |
| Postmark | No. No. A template library you edit into your own brand. |
| SendGrid | No. No. Templates and a design editor, but you supply the design. |
Inbound emailCan it receive and parse email sent to your domain?Nitrosend: Not a yes or no.Resend: Yes.Loops: No.MailerSend: Yes.Mailgun: Yes.SES: Yes.Postmark: Yes.SendGrid: Yes.
| Service | Answer |
|---|---|
| Nitrosend | Not a yes or no. An agent inbox on your own domain, enabled by request. |
| Resend | Yes. Yes, on every plan. |
| Loops | No. No inbound email in the documentation. |
| MailerSend | Yes. Yes, through inbound routing. |
| Mailgun | Yes. Yes, through inbound routes. |
| SES | Yes. Yes. SES receives mail through receipt rules and Mail Manager. |
| Postmark | Yes. Yes, with inbound processing on Pro and Platform. |
| SendGrid | Yes. Yes, with Inbound Parse. |
SDKs in five or more languagesDoes the service publish official SDKs in at least five programming languages?Nitrosend: No.Resend: Yes.Loops: No.MailerSend: Yes.Mailgun: Yes.SES: Yes.Postmark: Yes.SendGrid: Yes.
| Service | Answer |
|---|---|
| Nitrosend | No. No. Node and TypeScript only. Other languages call the REST API. |
| Resend | Yes. Yes. Official SDKs across languages, listed in its docs. |
| Loops | No. No. JavaScript, Go, PHP and Ruby, four in all. |
| MailerSend | Yes. Yes. Seven SDKs. |
| Mailgun | Yes. Yes. Official SDKs in six languages. |
| SES | Yes. Yes. The AWS SDKs cover every major language. |
| Postmark | Yes. Yes. Official libraries for Node.js and TypeScript, Python, Ruby, .NET, Java and PHP. Go is community-only. |
| SendGrid | Yes. Yes. SDKs in seven languages. |
SMTP relayCan a system that only speaks SMTP send through it?Nitrosend: No.Resend: Yes.Loops: Yes.MailerSend: Yes.Mailgun: Yes.SES: Yes.Postmark: Yes.SendGrid: Yes.
| Service | Answer |
|---|---|
| Nitrosend | No. No. Sending is through the API, the CLI and the MCP server. |
| Resend | Yes. Yes. An SMTP relay on every plan. |
| Loops | Yes. Yes. An SMTP service, with guides for Rails, Laravel and Supabase. |
| MailerSend | Yes. Yes. An SMTP relay. |
| Mailgun | Yes. Yes. An SMTP relay. |
| SES | Yes. Yes. An SMTP interface. |
| Postmark | Yes. Yes. SMTP alongside the API. |
| SendGrid | Yes. Yes. An SMTP relay. |
Yes answersOut of the questions that have a yes or no for that service6 of 8 yes for Nitrosend6 of 7 yes for Resend5 of 9 yes for Loops6 of 9 yes for MailerSend5 of 9 yes for Mailgun3 of 8 yes for SES5 of 8 yes for Postmark3 of 8 yes for SendGrid
At a glance
8 services, the same 7 tests, 100 points in all. In order: Nitrosend 83.75, Resend 77.5, Loops 73, MailerSend 68.5, Mailgun 67.5, SES 65.5, Postmark 64.5, SendGrid 59.5. Nitrosend has the best score on Works from your AI assistant, Receipts and newsletters on one plan, Emails in your brand, no designer and Developer tools. Every price and feature was read on each company's own pages on September 26, 2026.
When another service is the better pick
Nitrosend does not win every test. Two of the questions above, SDK languages and an SMTP relay, go against it. Read these before you choose it.
- Pick Resend if your backend is not Node and you only send transactional email. It scores 9 on developer tools, with official SDKs, an SMTP relay, inbound email and React Email on every plan.
- Pick Loops if you send a lot of email to a small audience. Every paid plan has unlimited sends, so a team sending only transactional email pays $49 a month at a million emails, against Nitrosend's $650. It also runs campaigns and workflows on the same plan, from a hosted MCP server and a CLI.
- Pick Postmark if you want the API to be boring and the delivery to be certain. It scores 9 on developer tools and 9 on track record, with official libraries for Node.js and TypeScript, Python, Ruby, .NET, Java and PHP, separate message streams and years of transactional sending at scale. There is no campaign builder or flows.
- Pick Amazon SES if you already live in AWS. It is $3.20 for 20,000 emails and $160 for a million on the Essentials plan, and the AWS SDKs cover every major language. The templates, suppression handling and reporting are yours to build.
- Pick Mailgun if routing and inbound matter most. Its inbound routes and validation API are strong, with official SDKs in six languages and a 9 on track record.
- Pick MailerSend or SendGrid if you need SDKs in seven languages and an SMTP relay on a familiar name. MailerSend lists both on its pricing page, and SendGrid's libraries cover C#, Go, Java, Node.js, PHP, Python and Ruby. SendGrid's free plan is now a trial of 100 emails a day for 60 days, and its Node package, @sendgrid/mail, has not had a release since September 19, 2025.
What each one costs in 2026
Most services here charge by emails sent. Amazon SES is metered per email. Loops charges by subscribed contacts, with sends unlimited on every paid plan, so a transactional-only sender pays for its smallest paid plan whatever the volume.
What sending costs
List prices, USD, monthly, September 26, 2026| Service | 20,000 emails a month | 1,000,000 emails a month |
|---|---|---|
| Nitrosend (pricing page) | $20Pro, contacts unlimited | $650Scale, contacts unlimited, including overage |
| Resend (pricing page) | $20Pro, which covers 50,000 | $650Scale |
| Loops (pricing page) | $49The 1,001 to 5,000 contacts plan, sends unlimited | $49Lowest. The same plan. Transactional sends are unlimited on every paid plan |
| MailerSend (pricing page) | $35Starter, the first plan with 50 webhooks and 250 templates. Hobby with overage is $29.50 but has 1 webhook and 10 templates | $600Starter |
| Mailgun (pricing page) | $33Basic, 10,000 included and $1.80 per 1,000 after | $700Scale |
| SES (pricing page) | $3.20Lowest. Essentials, the default for a new account, or $2 a la carte. Charged per email | $160Essentials, the default for a new account, or $100 a la carte. Charged per email |
| Postmark (pricing page) | $29.50Pro, 10,000 included and $1.30 per 1,000 after. Basic is $33 | $775Basic, the 1,500,000 plan. Pro is $852.50 |
| SendGrid (pricing page) | $19.95Essentials, which covers 50,000 | $799Pro, the 1,500,000 plan. The 700,000 plan is $499 |
At 20,000 emails a month, where most teams start, Nitrosend is $20. Amazon SES is $3.20, SendGrid $19.95, Resend $20, Postmark $29.50, Mailgun $33, MailerSend $35 and Loops $49.
At a million emails a month, Nitrosend is $650. MailerSend is $600, Resend $650, Mailgun $700, Postmark $775 and SendGrid $799. Loops is $49 for transactional email, though its price climbs with every subscribed contact once you send newsletters too. Amazon SES is $160, and the product layer is yours to build.
The $20 buys more than sending. Nitrosend's developer page says most email APIs stop at "send a message", and Nitrosend provides the entire stack through the same key: lists, segments, automated flows, brands, templates and deliverability, alongside a single-call transactional send. If you would otherwise buy a second product for campaigns, add the two bills together before you compare.
How we scored
Every service gets a score out of 10 on the same seven tests used on the email API service rankings. Each test is worth a set number of points, 100 in all. Working from your AI assistant is worth the most, 25 points, because that is where email is heading. Price, developer tools and track record, where the older services are strongest, share 40 points, so a service that is better there gets full credit for it.
Each test is a question with one answer per service, checked against the service's own pages on September 26, 2026. A 10 means it does the job fully on its normal plans. A 5 means it does part of it, or only on a higher plan or in a second product.
Works from your AI assistant, 25 points. Can an agent inside Claude, ChatGPT, Cursor or Codex go from nothing to a delivered transactional email, and then read back what happened to it, with no person opening the web app along the way? Scored on the first-party MCP server and what its tools cover, a CLI that works in a non-interactive runner, account and sender setup over the API, and listings in the chat apps people already work in. Scored on one written rule for every vendor: a first-party server the vendor runs and that can send counts fully; a third-party wrapper (Zapier, Composio, Kanopi, community servers) counts for less; a server that only drafts or reads counts for less than one that sends.
Receipts and newsletters on one plan, 15 points. Can receipts and password resets, and the newsletters and automated flows that follow them, go out from one account, on one bill, through one API, with the two streams kept apart?
Emails in your brand, no designer, 10 points. Does the product produce the receipt, reset and welcome emails in your brand's own logo, colors, fonts and voice, or does a developer have to write or buy the HTML template first?
Free plan, 10 points. How far can a developer get on the free plan before paying: the monthly volume, the daily ceiling, any one-off starter allowance, and whether the plan is perpetual or a trial that ends.
Price, 15 points. What does sending cost at 20,000 emails a month, where most teams start, and at 1,000,000, where a busy product ends up? Scored on list prices in US dollars, paid monthly, at the cheapest plan that covers the volume. Every ranking on this site uses the same fixed scale. At 20,000 emails, $20 or less scores 10, then $25 scores 9, $32 scores 8, $40 scores 7, $50 scores 6, $70 scores 5, $100 scores 4 and $140 scores 3. At 1,000,000, $500 or less scores 10, then $625, $800, $1,000, $1,250, $1,750, $2,500 and $3,500 step down the same way. Anything dearer, or a price given only by quote, scores 2. The score is the average of the two.
Developer tools, 15 points. How complete is what a developer builds on: a REST API with an OpenAPI spec, official SDKs across languages, a CLI, an SMTP relay, documented delivery-event webhooks, idempotent sends, a test or sandbox mode, inbound email handling, and how deep the reference docs go?
Track record and support, 10 points. How long has it run transactional sending at scale, which deliverability controls can you own (dedicated IPs, suppression, separate streams, a published uptime SLA), and what support comes with the plan?
One thing is not scored: inbox placement. No two of these services publish a comparable deliverability number, so a score there would be a guess dressed up as a measurement.
Why the first send takes so long
Email is slower to first value than almost any other developer tool, and the cause is the setup, not the code. Before a real message goes out, most services ask for an API key, DNS records, a wait for them to propagate, a verified domain and often a review queue. A payments API such as Stripe hands you a sandbox with test keys and test cards whose charges move no money, so the first call works before anything is live. Email test modes let you write the code too, but real delivery still waits on the domain, which is why the domain step, not the code, is where most first sends stall.
Nitrosend removes the DNS wait from the first send. An agent or a script can create the account with POST /v1/signup, mint a key, activate a reserved sender on a subdomain Nitrosend already owns and has already verified, then send with POST /v1/my/messages and an Idempotency-Key header. Your own domain comes later, when you want your own reputation. The quickstart walks through it, and the CLI does the same from a terminal.
Every other service here needs a person to sign up and verify a domain or a sender address before real mail leaves. Most offer a test mode, so you can write the code while DNS propagates.
What to test in your first hour
Feature lists do not predict how an API feels at 2am. Run these on any two candidates.
- Send one message from a fresh account. Note how long it takes, and whether a person had to verify a domain first.
- Send a deliberately broken request. Read the error. An error that only says a send was blocked sends a developer round in circles, retrying the call, checking billing and rechecking DNS, when one line naming the cause would end it. RFC 9457 is the standard for carrying machine-readable error details in an API response, and whatever format a service uses, the error should name the field and say what to fix. Nitrosend's REST errors return a code with the failing field listed, and its Node SDK throws typed errors, so you branch on
ValidationErrororNotFoundErrorrather than matching a message. - Push a burst through it. Watch the acceptance rate, which is the subject of the best email sending API rankings.
- Trigger a webhook. Check whether it is signed, retried and replayable, and whether it follows Standard Webhooks, a shared signing format with ready-made verification libraries, so you do not hand-roll the signature check. Nitrosend's webhooks use that format. Webhooks are where most integrations break.
- Break a transactional send on purpose. Then check that something tells you. A password reset that never arrives raises no error in your app, so a team may not notice its receipts stopped after an API change. Google's SRE book calls this black-box monitoring, testing externally visible behavior as a user would see it: find the failure event you would alert on before you need it.
- Send with the same idempotency key twice. You should get one email, not two.
- Ask your coding assistant to find the docs for an integration you need. A coding agent now fetches a library's documentation to get an API call right, so a missing page costs you twice: you cannot find it, and neither can the agent writing your code.
That hour predicts the next two years better than any comparison table, this one included. If you are choosing between two services, the head-to-head Nitrosend and Resend comparison goes test by test.
Add one test the table cannot show: run the same job from the agent you already use. George Hartley, Nitrosend's co-founder, wrote on LinkedIn in September 2026: "Building an agent first tool is wild. You ship one MCP server and your product turns up in places you haven't been yet". On SaaS Stories the same month he gave the design rule behind it: "we've built it to be completely agent first and MCP first. So you are only limited by how smart your agent is because everything that you need to do can be completely driven by the MCP." If a service's MCP server only sends, your agent hits a wall the first time it needs a contact list, a template or a bounce report.
Email API for developers FAQ
Nitrosend, with the top score in this review, 83.75 out of 100. It is the only service here where an AI assistant can create the account, get a ready sender and make the first send without a person verifying a domain, and its typed Node SDK, CLI and MCP server cover the whole platform, from $20 a month. Pick Resend if your backend is not Node and you want official SDKs across languages, or Postmark if delivery certainty matters more than anything else.
Resend, Postmark, MailerSend, SendGrid and Mailgun each publish official SDKs in six or more languages, and Amazon SES is covered by every AWS SDK. Nitrosend's first-party SDK is Node and TypeScript only, so a Ruby, Go, PHP or .NET backend calls its REST API directly. Its REST API ships an OpenAPI spec, so those backends can generate a typed client. A team on the Vercel AI SDK can use @nitrosend/ai-sdk, which exposes Nitrosend's MCP server as AI SDK tools.
Resend, then Postmark. Resend's docs open with quickstarts for Node.js, PHP, Python, Ruby, Go, Java, Rust, Elixir and .NET, and Postmark documents official libraries for Node.js and TypeScript, Python, Ruby, .NET, Java and PHP. Nitrosend publishes its whole reference as one file for AI assistants to read, at docs.nitrosend.com/llms-full.txt, following the llms.txt proposal, and an OpenAPI 3.1 spec.
On Nitrosend, in minutes, because the first send goes out from a sender on a subdomain Nitrosend has already verified. Everywhere else, the API call takes minutes and the verified domain takes as long as DNS takes. A test mode lets you write the code while you wait.
Nitrosend, with 9 out of 10 on working from your AI assistant. An agent can create the account with POST /v1/signup, mint a key, activate a sender Nitrosend has already verified and send, all without a person opening the web app. Resend, Loops and MailerSend score 8 with hosted MCP servers, but on each of them a person signs up first; Resend's own agent guide says a human must create the account. SendGrid scores 3, because Twilio's own MCP server is read-only: it searches the docs and does not send.
Add Nitrosend's MCP server. In Claude Code, run claude mcp add --transport http nitrosend https://api.nitrosend.com/mcp; in Claude Desktop and Claude.ai, use the Nitrosend connector under Settings, Connectors; in ChatGPT, Cursor or Codex, add the same server URL. Sign in when the OAuth window opens, then ask for the email. A transactional message goes out on the call, while a campaign or flow waits as a draft until the account owner approves it. The MCP docs list every tool.
No. Nitrosend sends through its API, its CLI and its MCP server. A legacy system that only speaks SMTP needs one of the other services here, or it can keep its current provider underneath Nitrosend with bring-your-own sending keys.
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