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 AI agents of the seven reviewed here, with the top score of 83.75 out of 100. It is the only one here where your agent in Claude, ChatGPT, Cursor or Codex can sign up, get a ready sender and send to anyone without a person opening a dashboard. AgentMail also lets an agent sign itself up, but a person has to pass on a one-time code before it can email anyone else. To send email from an AI agent with Nitrosend, connect its MCP server at api.nitrosend.com/mcp, sign in with OAuth, and ask the agent to send. Its 28 tools run contacts, segments, flows, campaigns and reporting as well as sending, and a campaign or flow waits for an approve step before it goes out. Your receipts and newsletters go out from one account, in your brand, from $20 a month for 20,000 emails. Resend comes next at 77.5, then Mailgun at 67.5.
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 3Mailgun
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 4Amazon 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 5Postmark
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 6SendGrid
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).
Rank 7AgentMail
54 out of 100Total
- Priced by
- Inboxes and emails sent
- Free plan
- 3 inboxes, 3,000 emails a month, no card
- Entry plan
- $20 a month, 10 inboxes, 10,000 emails (Developer)
- Works from your AI assistant8 out of 10Hosted MCP server with OAuth and a sign-up API for agents, but a person must pass on a one-time code before the account can email anyone else (docs).
- Receipts and newsletters on one plan2 out of 10Built for two-way agent conversations. No campaigns, newsletters, segments or automation flows are documented (docs).
- Emails in your brand, no designer2 out of 10No email templates or brand tools are documented. The agent or developer writes every body (docs).
- Free plan7 out of 103 inboxes and 3,000 emails a month, 100 a day, no card, but no custom domain on the free plan (pricing).
- Price5 out of 10$40 a month for 20,000 emails on Developer with add-ons, and no public price for a million (pricing).
- Developer tools7 out of 10Python and Node SDKs, a CLI, SMTP and IMAP, delivery webhooks, WebSockets and first-class inbound, but no templates or test mode (docs).
- Track record and support4 out of 10Y Combinator-backed, with a $6M seed announced in March 2026. SOC 2, but dedicated IPs and an SLA only on Enterprise (pricing).
How they compare
How each one scores
Scores out of 10, September 26, 2026| What we compared | Nitrosend | Resend | Mailgun | SES | Postmark | SendGrid | AgentMail |
|---|---|---|---|---|---|---|---|
| Works from your AI assistant25 points | 9 out of 10 | 8 out of 10 | 6 out of 10 | 7 out of 10 | 6 out of 10 | 3 out of 10 | 8 out of 10 |
| Receipts and newsletters on one plan15 points | 9 out of 10 | 7 out of 10 | 4 out of 10 | 3 out of 10 | 4 out of 10 | 6 out of 10 | 2 out of 10 |
| Emails in your brand, no designer10 points | 9 out of 10 | 6 out of 10 | 5 out of 10 | 2 out of 10 | 5 out of 10 | 5 out of 10 | 2 out of 10 |
| Free plan10 points | 7 out of 10 | 8 out of 10 | 7 out of 10 | 4 out of 10 | 4 out of 10 | 3 out of 10 | 7 out of 10 |
| Price15 points | 8.5 out of 10 | 9 out of 10 | 8 out of 10 | 10 out of 10 | 8 out of 10 | 9 out of 10 | 5 out of 10 |
| Developer tools15 points | 10 out of 10 | 9 out of 10 | 9 out of 10 | 9 out of 10 | 9 out of 10 | 9 out of 10 | 7 out of 10 |
| Track record and support10 points | 4 out of 10 | 6 out of 10 | 9 out of 10 | 9 out of 10 | 9 out of 10 | 8 out of 10 | 4 out of 10 |
| Total scoreout of 100 | 83.75 out of 100,1st | 77.5 out of 100,2nd | 67.5 out of 100,3rd | 65.5 out of 100,4th | 64.5 out of 100,5th | 59.5 out of 100,6th | 54 out of 100,7th |
Here are the seven yes-or-no questions teams usually ask before they hand email to an agent. 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.
7 services, side by side
Checked September 26, 2026QuestionNitrosendResendMailgunSESPostmarkSendGridAgentMail
NitrosendResendMailgunSESPostmarkSendGridAgentMailSend from the chatCan an agent send a transactional email without anyone opening the web app?Nitrosend: Yes.Resend: Yes.Mailgun: Yes.SES: Not a yes or no.Postmark: Yes.SendGrid: Not a yes or no.AgentMail: Yes.
| 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. |
| 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. |
| AgentMail | Yes. Yes, through the hosted MCP server's send_message tool once an account exists. |
Hosted MCP serverCan a chat app connect over the web, with no local install?Nitrosend: Yes.Resend: Yes.Mailgun: No.SES: No.Postmark: No.SendGrid: No.AgentMail: Yes.
| 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. |
| 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. |
| AgentMail | Yes. Yes. mcp.agentmail.to/mcp, with OAuth or an API key. |
Sign up with no personCan an agent create the account and send a first email with no DNS work?Nitrosend: Yes.Resend: No.Mailgun: No.SES: No.Postmark: No.SendGrid: No.AgentMail: Not a yes or 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. |
| 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. |
| AgentMail | Not a yes or no. An agent can sign itself up over the API, but a person must supply the emailed one-time code before it can send to anyone else. |
Campaigns and flows in the same planDo newsletters and automations come with the transactional plan?Nitrosend: Yes.Resend: Not a yes or no.Mailgun: No.SES: No.Postmark: Not a yes or no.SendGrid: No.AgentMail: 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. |
| 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. |
| AgentMail | No. No campaigns, newsletters or automation flows are documented. |
Perpetual free planIs there a free plan that does not run out?Nitrosend: Yes.Resend: Yes.Mailgun: Yes.SES: No.Postmark: Yes.SendGrid: No.AgentMail: Yes.
| 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. |
| 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. |
| AgentMail | Yes. Yes. 3,000 emails a month at $0 with no card and no stated end date. |
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.Mailgun: No.SES: No.Postmark: No.SendGrid: No.AgentMail: 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. |
| 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. |
| AgentMail | No. No template or brand features are documented. |
Inbound emailCan it receive and parse email sent to your domain?Nitrosend: Not a yes or no.Resend: Yes.Mailgun: Yes.SES: Yes.Postmark: Yes.SendGrid: Yes.AgentMail: 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. |
| 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. |
| AgentMail | Yes. Yes. Receiving, threading and replies are the core of the product, over webhooks, WebSockets or IMAP. |
Yes answersOut of the questions that have a yes or no for that service6 of 6 yes for Nitrosend4 of 5 yes for Resend3 of 7 yes for Mailgun1 of 6 yes for SES3 of 6 yes for Postmark1 of 6 yes for SendGrid4 of 6 yes for AgentMail
At a glance
7 services, the same 7 tests, 100 points in all. In order: Nitrosend 83.75, Resend 77.5, Mailgun 67.5, SES 65.5, Postmark 64.5, SendGrid 59.5, AgentMail 54. 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. Read these before you choose it.
- Pick AgentMail if your agent needs its own inbox. It is built for two-way conversations: an agent can sign itself up over the API and get an inbox on a domain AgentMail already owns, then send, receive, reply and search over a hosted MCP server. It scores an 8 on working from your AI assistant, level with Resend. A person still passes on a one-time code before the account can email anyone else, and it has no campaigns, flows or templates. Nitrosend has agent inboxes of its own.
- Pick Resend if the agent only sends well-built transactional email. It scores an 8 on working from your AI assistant, with a hosted MCP server, a CLI built for agents and installable skills, and it scores 9 on developer tools. A person verifies a domain before the first send. See Nitrosend and Resend compared.
- Pick Mailgun if the agent has to read replies as well as send. It scores a 9 on developer tools and on track record, and it parses inbound mail and routes it to your application. See Nitrosend and Mailgun compared.
- Pick Postmark if the agent sends password resets and nothing else. It scores a 9 on track record and support, and publishes an MCP server you run yourself. See Nitrosend and Postmark compared.
- Pick Amazon SES if the agent sends at volume and you build the rest. It is $3.20 for 20,000 emails and $160 for a million, which earns it a 10 on price. See Nitrosend and Amazon SES compared.
- Pick SendGrid if you already run on Twilio. It has the widest scale headroom here, but every SendGrid server on the official MCP registry's SendGrid listing is community built. See Nitrosend and SendGrid compared.
What each one costs in 2026
An agent sends in bursts, and a retry loop can send more than you planned, so the price at volume matters more here than on most pages. Every service here charges by emails sent except Amazon SES, which is metered, at $0.10 per 1,000 a la carte or $0.16 per 1,000 on the Essentials plan that new accounts default to since July 21, 2026. AgentMail also charges for inboxes.
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 |
| 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 | $160Lowest. Essentials, 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 |
| AgentMail (pricing page) | $40Developer, 10,000 included and $2 per 1,000 extra as an add-on. Startup is $200 | Ask salesNot self-serve. Startup is capped at 150,000 a month |
At 20,000 emails a month, Nitrosend is $20, the same as Resend and a nickel more than SendGrid at $19.95. Postmark is $29.50, Mailgun $33 and AgentMail $40 on Developer with extra emails added.
At a million emails a month, Nitrosend is $650. Resend is $650, Mailgun $700, Postmark $775 and SendGrid $799. AgentMail sends that volume only on a sales plan. With Amazon SES the templates, unsubscribe handling and reporting are yours to build.
What the $20 buys is the part an agent needs after the send: contacts, segments, flows, campaigns and reporting on the same key, and an Idempotency-Key on every send so a retry cannot become a second email. That header is the one the IETF Idempotency-Key draft describes for making a POST safe to retry, and Nitrosend's MCP send tool will not make a live send without one, which matters when the caller is an agent that retries on its own.
How we scored
Every service gets a score out of 10 on the same seven tests. Each test is worth a set number of points, 100 in all. Working from your AI assistant is worth the most, 25 points, and on this page it is the test to read first: whether an agent can go from nothing to a delivered email, and read back what happened, with no person opening the web app. It carries the most points because the buyer on this page is handing email to an agent, and every step that needs a person in a web app is a step the agent cannot finish. Price, developer tools and track record 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.
What is not on this list, and why
Nylas was on the earlier version of this page and is not scored here. Its main product is an API over your users' existing Gmail, Outlook and IMAP mailboxes, priced per connected account, so the mail goes out through each user's own provider and a price per email does not apply. It has a hosted MCP server with 38 tools and a one-line install for Claude Code and Codex, and it is the right pick if your agent works inside people's own inboxes rather than sending from yours. Its sending from a verified domain is in beta and is not on its pricing page (docs).
Sending email from an agent, or running it
An email API for AI agents is one an autonomous system can operate for you: not only sending a message, but writing it, choosing who gets it, reading back what happened, and stopping when it should. Most email APIs support the first of those. This page is decided by the other three.
An agent that can send email needs one tool. Almost every provider offers that now, and several ship an MCP server that does little else. An agent that can run your email has to manage contacts, build a segment, write and render the email, schedule a campaign, read the delivery events and act on a bounce. That is dozens of operations, not one. Nitrosend exposes 28 nitro_* tools over MCP for that job. A campaign or flow is saved as a draft and goes out only after a separate approve step, and a one-off transactional email sends at once with an idempotency key, so a retry cannot send it twice. Email MCP, defined and what MCP is cover the protocol, and agentic email covers the category.
Nitrosend's own traffic shows which kind of agent is arriving. Co-founder George Hartley said on SaaS Stories in September 2026: "94% of our usage is via the MCP from an agent doing stuff. So, you know, 19 out of 20 things that are done is actually an AI agent doing it on Nitrosend." A month earlier, on The Breakout CEO, he put the scale of it this way: "instead of 8 billion people, there's a hundred billion agents running companies. They all need this." He had said it in July on X: "Soon there'll be 100 billion AI agents. Every one of them needs email." That is why this list scores how well an agent can run your email, not only whether it can send one message.
Running email from an agent means deciding what the agent may do alone and what waits for a person. The MCP tools specification says there should always be a human in the loop with the ability to deny a tool call, so the useful question is where each service draws that line. Nitrosend draws it between a single message, which sends at once, and anything going to a list, which waits for an approve step. Sign-in is the other difference. The MCP authorization specification builds remote servers on OAuth 2.1, so a hosted server lets an agent connect through a browser sign-in instead of a person pasting an API key into a config file. Nitrosend, Resend and AgentMail work that way. The Postmark and Mailgun servers run on your machine with a key.
The other question is who opens the account. On most services a person signs up, verifies a domain at a registrar and pastes a key into the agent. On Nitrosend the agent can create the account and get a ready sender over HTTP, and the Nitrosend MCP server takes over from there. Email for agents walks through the path, and the Claude Code integration shows it in one client.
The thing nobody warns you about
If the agent writes the email as well as sending it, know what you are trusting. A general-purpose model will write a fluent welcome sequence, but it does not know which mailbox-provider rules apply unless something tells it. The rules are public. Google's email sender guidelines require one-click unsubscribe on marketing mail for anyone sending more than 5,000 messages a day, ask senders to keep the spam rate in Postmaster Tools below 0.3%, and say not to put promotions in a sales receipt. That last rule is the one an agent breaks most easily: ask it to add an upsell to an order confirmation and it has no reason to refuse. Nitrosend's Claude plugin ships an email marketing skill next to the send tools, so the agent works from a written reference rather than memory.
So let the agent's freedom follow how reversible the step is. Drafting an email can be undone. Sending to 40,000 people cannot. Whatever you pick from this list, keep a person on the step that cannot be undone, and keep your transactional and marketing streams apart so an agent trying out a campaign cannot touch a password reset.
Email API for AI agents FAQ
Nitrosend, with the top score in this review, 83.75 out of 100. It is the only service here where an agent can sign up, get a ready sender and send to anyone without a person opening a dashboard, and its 28 MCP tools cover contacts, segments, flows, campaigns and reporting, with an approve step before a campaign or flow goes out. Pick AgentMail if your agent needs its own inbox, and Resend if it only sends transactional email.
Yes. Nitrosend, Resend and AgentMail host MCP servers with OAuth sign-in, so a chat app connects over the web. Postmark and Mailgun publish servers you run yourself, and AWS's own managed MCP server can send through Amazon SES on IAM credentials a person sets up. Every SendGrid server on the official MCP registry's SendGrid listing is community built. Email MCP, defined covers what a server exposes.
On two services here, partly. Nitrosend publishes account creation over HTTP and a ready sender on a domain it already owns, so the whole path needs no person. AgentMail publishes an agent sign-up endpoint and puts inboxes on its own domain, then sends a one-time code to a person to unlock sending to anyone else. Everywhere else a person signs up and verifies a domain at a registrar.
Only with a gate on the step that cannot be undone. On Nitrosend a campaign or flow is a draft until a separate approve step, so a person can sign off before a list gets anything, the way the MCP tools specification asks clients to keep a human able to deny a tool call. A one-off transactional email sends at once, and its required idempotency key stops a retry from sending it twice. If your provider has no approval step, build one into your own setup before you connect an agent to a list.
On Nitrosend, yes, including contacts, segments, templates, flows, campaigns and domains. On most services here the agent can send and read events, and the rest of the account stays in a dashboard. That gap is what the 25-point test on this page measures.
Nitrosend, with a 9 out of 10 on working from your AI assistant, the heaviest test on this page. It connects to Claude, Claude Code, ChatGPT, Cursor, Codex and Gemini over MCP, and an agent can sign up and send with no dashboard. AgentMail and Resend score 8. Both host MCP servers with OAuth sign-in, but on Resend a person verifies a domain first, and on AgentMail a person enters a one-time code before the agent can email anyone else. See the Claude Code integration.
In Claude or Claude Desktop, turn on the official Nitrosend connector under Settings, then Connectors, and sign in. In Claude Code, run claude mcp add --transport http nitrosend https://api.nitrosend.com/mcp and sign in with OAuth when it asks, or point Claude Code at nitrosend.com/SKILL.md and it runs the setup itself. Then ask Claude to send the email. A one-off message goes out at once, and a campaign waits for your approval. ChatGPT connects through its plugin directory and Cursor through /add-plugin nitrosend. The Claude setup guide has every step.
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