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 SaaS teams that run their email from AI agents. It has the top score of the seven reviewed here, 83.75 out of 100, and scores 9 out of 10 on the heaviest test, working from your AI assistant. Your product notifications and your lifecycle emails run on separate streams in one account, on one plan and one bill, with unlimited contacts on every plan. It is the only one of the seven here that your AI assistant, whether Claude, ChatGPT, Cursor or Codex, can sign up to and send from without anyone opening a dashboard, and it writes every email in your brand. To send from an agent, add the MCP server at api.nitrosend.com/mcp, sign in with OAuth and ask for the email: a product email goes out on one call, and a campaign or flow sends only once it has been approved. It costs $20 a month for 20,000 emails and $650 for a million emails on Scale including overage. Resend comes next at 77.5, then Loops at 73 and Brevo at 70.
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 4Brevo (formerly Sendinblue)
70 out of 100Total
- Priced by
- Emails sent
- Free plan
- 300 emails a day, no expiry
- Entry plan
- Starter, $9 a month, 5,000 emails
- Works from your AI assistant5 out of 10Hosted MCP server at mcp.brevo.com with a token a person creates, but its modules list no tool that sends a transactional email (docs).
- Receipts and newsletters on one plan8 out of 10Transactional email by API and SMTP on every plan, counted in the same monthly volume as campaigns, with automation from Standard (pricing).
- Emails in your brand, no designer7 out of 10The brand library fetches a logo, colors, fonts and social links from your website into the email editor, but not a tone of voice (help).
- Free plan9 out of 10300 emails a day, about 9,000 a month, with transactional email and up to 100,000 contacts, free forever (help).
- Price6 out of 10$69 a month for 20,000 emails on Standard, the first plan with automated emails (Starter is $32 without them), and $999 for a million on Professional (pricing).
- Developer tools9 out of 10Official SDKs in seven languages, an SMTP relay, transactional webhooks, a sandbox header and inbound email parsing (docs).
- Track record and support7 out of 10Sending since 2012 as Sendinblue. Dedicated IPs are an add-on from Professional, and an SLA comes only with Enterprise (help).
Rank 5Customer.io
68 out of 100Total
- Priced by
- Profiles (people and objects)
- Free plan
- None. 14-day trial, 5,000 messages
- Entry plan
- $100 a month, 5,000 profiles, 1M emails
- Works from your AI assistant8 out of 10Hosted MCP server with OAuth, a Claude connector, ChatGPT and Cursor plugins and a CLI that can sign up, but every account is reviewed by a person before it sends (docs).
- Receipts and newsletters on one plan8 out of 10Transactional API, broadcasts and journeys on one Essentials plan with a separate transactional IP pool, though sending and data go through separate APIs (pricing).
- Emails in your brand, no designer8 out of 10Design Studio reads your website to generate styles and a brand document that its AI writing follows (docs).
- Free plan2 out of 10No free plan. A 14-day trial with 5,000 messages, or a year free for startups that raised under $10M (docs).
- Price6 out of 10$100 a month at 5,000 profiles and about $955 at 100,000, with 1,000,000 emails included on Essentials (pricing).
- Developer tools6 out of 10Node, Python and Go data libraries, mobile SDKs, reporting webhooks and test sends, but no SMTP relay into it and no inbound email (docs).
- Track record and support8 out of 10Running since 2012 for 9,000+ brands, with a transactional IP pool, dedicated IPs at $50 each, SOC 2 and HIPAA (docs).
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).
How they compare
How each one scores
Scores out of 10, September 26, 2026| What we compared | Nitrosend | Resend | Loops | Brevo | Customer.io | SES | Postmark |
|---|---|---|---|---|---|---|---|
| Works from your AI assistant25 points | 9 out of 10 | 8 out of 10 | 8 out of 10 | 5 out of 10 | 8 out of 10 | 7 out of 10 | 6 out of 10 |
| Receipts and newsletters on one plan15 points | 9 out of 10 | 7 out of 10 | 9 out of 10 | 8 out of 10 | 8 out of 10 | 3 out of 10 | 4 out of 10 |
| Emails in your brand, no designer10 points | 9 out of 10 | 6 out of 10 | 5 out of 10 | 7 out of 10 | 8 out of 10 | 2 out of 10 | 5 out of 10 |
| Free plan10 points | 7 out of 10 | 8 out of 10 | 7 out of 10 | 9 out of 10 | 2 out of 10 | 4 out of 10 | 4 out of 10 |
| Price15 points | 8.5 out of 10 | 9 out of 10 | 8 out of 10 | 6 out of 10 | 6 out of 10 | 10 out of 10 | 8 out of 10 |
| Developer tools15 points | 10 out of 10 | 9 out of 10 | 7 out of 10 | 9 out of 10 | 6 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 | 7 out of 10 | 8 out of 10 | 9 out of 10 | 9 out of 10 |
| Total scoreout of 100 | 83.75 out of 100,1st | 77.5 out of 100,2nd | 73 out of 100,3rd | 70 out of 100,4th | 68 out of 100,5th | 65.5 out of 100,6th | 64.5 out of 100,7th |
Here are the seven yes-or-no questions SaaS teams 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.
7 services, side by side
Checked September 26, 2026QuestionNitrosendResendLoopsBrevoCustomer.ioSESPostmark
NitrosendResendLoopsBrevoCustomer.ioSESPostmarkSend from the chatCan an agent send a transactional email without anyone opening the web app?Nitrosend: Yes.Resend: Yes.Loops: Yes.Brevo: Not a yes or no.Customer.io: Yes.SES: Not a yes or no.Postmark: 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. |
| Loops | Yes. Yes, a published transactional email, once a person has signed in and connected the MCP server. |
| Brevo | Not a yes or no. The hosted MCP server creates and manages campaigns, but no tool for sending a transactional email is documented. |
| Customer.io | Yes. Yes, through the hosted MCP server with the live-send scope, after the account passes manual review. |
| 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. |
Hosted MCP serverCan a chat app connect over the web, with no local install?Nitrosend: Yes.Resend: Yes.Loops: Yes.Brevo: Yes.Customer.io: Yes.SES: No.Postmark: 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. |
| Brevo | Yes. Yes. mcp.brevo.com, signed in with a token a person generates in the web app. |
| Customer.io | Yes. Yes. mcp.customer.io/mcp, with OAuth and scoped permissions. |
| SES | No. No hosted SES MCP server. |
| Postmark | No. No. The official server runs locally through npx with an API token. |
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.Brevo: No.Customer.io: No.SES: No.Postmark: 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. |
| Brevo | No. No. A person creates the account and the MCP token, and Brevo approves the account before it sends. |
| Customer.io | No. No. The CLI can start a signup, but every account is reviewed by hand before it can send. |
| 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. |
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.Brevo: Yes.Customer.io: Yes.SES: No.Postmark: Not a yes or 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. |
| Brevo | Yes. Yes. Transactional is on every plan and automation runs from Free up to 2,000 contacts and from Standard without a limit. |
| Customer.io | Yes. Yes. Transactional, broadcasts and journeys are all on Essentials. |
| 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. |
Perpetual free planIs there a free plan that does not run out?Nitrosend: Yes.Resend: Yes.Loops: Yes.Brevo: Yes.Customer.io: No.SES: No.Postmark: 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. |
| Loops | Yes. Yes. 4,000 sends in any 30 days, with a Loops footer. |
| Brevo | Yes. Yes. 300 emails a day with no time limit. |
| Customer.io | No. No. A 14-day trial, or 12 months free for qualifying startups. |
| 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. |
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.Brevo: Yes.Customer.io: Yes.SES: No.Postmark: 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. |
| Brevo | Yes. Yes. The brand library fetches logo, colors, fonts and links from a URL, not tone of voice. |
| Customer.io | Yes. Yes. Design Studio scrapes your website to generate styles and a brand document. |
| SES | No. No. Templates are HTML you write. |
| Postmark | No. No. A template library you edit into your own brand. |
Inbound emailCan it receive and parse email sent to your domain?Nitrosend: Not a yes or no.Resend: Yes.Loops: No.Brevo: Yes.Customer.io: No.SES: Yes.Postmark: 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. |
| Brevo | Yes. Yes. Inbound parsing posts replies to your webhook as JSON. |
| Customer.io | No. No. Inbound handling covers SMS and WhatsApp replies, not email. |
| SES | Yes. Yes. SES receives mail through receipt rules and Mail Manager. |
| Postmark | Yes. Yes, with inbound processing on Pro and Platform. |
Yes answersOut of the questions that have a yes or no for that service6 of 6 yes for Nitrosend4 of 5 yes for Resend4 of 7 yes for Loops5 of 6 yes for Brevo4 of 7 yes for Customer.io1 of 6 yes for SES3 of 6 yes for Postmark
At a glance
7 services, the same 7 tests, 100 points in all. In order: Nitrosend 83.75, Resend 77.5, Loops 73, Brevo 70, Customer.io 68, SES 65.5, Postmark 64.5. 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. Read these before you choose it.
- Pick Resend if product email is the whole job and your team lives in code. It scores 9 on developer tools, with official SDKs across languages, an SMTP relay, inbound email and React Email, all listed on Resend's pricing page. See Nitrosend and Resend compared.
- Pick Brevo if you want the biggest free plan while you find product-market fit. It scores a 9 on free plan, with a free plan that does not expire and sends up to 300 emails a day, and a 9 on developer tools. It is $32 for 20,000 emails on Starter, but $999 for a million.
- Pick Loops if you want product and marketing email on one flat price while your list is small. Transactional email to people who are not on your list is unlimited on every paid plan, because those recipients are not added to your audience and do not count toward billing, so $49 a month covers any volume of product email. It scores an 8 on price against Nitrosend's 10. Campaigns and workflows share the plan, and the price climbs with your subscribed list. See Nitrosend and Loops compared.
- Pick Customer.io if lifecycle journeys run your growth and you have the budget. It scores an 8 on track record and on brand, with journeys, a separate transactional IP pool and a design studio that reads your website to write a brand document. There is no free plan, though startups that have raised under $10M can apply for a year free. Otherwise it is $100 a month at 5,000 profiles and about $955 at 100,000.
- Pick Postmark if product email reliability is the only thing that matters. It scores a 9 on track record and support, with message streams that keep bulk mail away from resets. You add a separate tool for marketing. See Nitrosend and Postmark compared.
- Pick Amazon SES if you will build the rest yourself. It is $3.20 for 20,000 emails and $160 for a million on Essentials, which earns it a 10 on price, and it scores a 9 on developer tools and on track record. See Nitrosend and Amazon SES compared.
What each one costs in 2026
A SaaS keeps every signup and mails an active fraction of them, so how a service prices matters as much as the number. Nitrosend, Resend, Brevo and Postmark charge by emails sent. Amazon SES is metered per email. Loops and Customer.io charge by contacts. Loops makes transactional email to people not on your list unlimited on any paid plan, so its figure is the smallest paid plan, and it climbs as your subscribed list grows. Customer.io counts everyone you email as a profile, so it is shown at 5,000 and 100,000 profiles.
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 |
| Brevo (pricing page) | $69Standard, the first plan with automation. Starter is $32 without it | $999Professional. Standard stops at 500,000 emails |
| Customer.io (pricing page) | $100Essentials, 5,000 profiles and 1,000,000 emails included | $955Essentials at 100,000 profiles, $100 plus 95,000 extra profiles at $0.009, 1,000,000 emails included |
| 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 |
At 20,000 emails a month, Nitrosend is $20, the same as Resend. Postmark is $29.50, Loops $49, Brevo $69 on Standard and Customer.io $100 for 5,000 profiles. Brevo is priced at Standard because it is the first plan with automated emails, the fair comparison with Nitrosend's $20 (Starter is $32 without them).
At a million emails a month, Nitrosend is $650. Resend is $650, Postmark $775, Customer.io about $955 at 100,000 profiles and Brevo $999. Amazon SES is $160, with campaigns, automated flows and an email editor yours to build. Loops stays at $49 for product email to people not on your list, and rises with every subscriber you add to its marketing list.
On Nitrosend, contacts are unlimited on every plan, so a growing user base does not move the bill. What moves it is how much you send. The same plan carries product email, campaigns and flows, so there is no second product to add to the comparison.
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, because that is where email is heading: MCP, the open standard assistants use to reach outside tools, now sits with the Linux Foundation and has been adopted by Claude, ChatGPT, Cursor, Gemini and Microsoft Copilot. Receipts and newsletters on one plan is worth 15, and matters more to a SaaS than to most. 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 makes email for SaaS different
A SaaS product sends two kinds of email from day one: product notifications set off by the application, and lifecycle email meant to get people using it. Most teams buy two vendors for this, and the seam between them is where SaaS email goes wrong.
The seam matters more once an agent is doing the work. George Hartley, Nitrosend's co-founder, described the job most SaaS email tools still cannot do on SaaS Stories in September 2026: "if you're setting up an onboarding flow and you have maybe sort of seven key customer types and they all have kind of different personalization ... you can't say right now for most ... existing systems ... look at our last two years of kind of how we've nurtured trial through to paid ... are our flows correct ... recut them all". That is the test to put to any service on this list: can your agent read how trials actually convert and rebuild the lifecycle flows from it, in the same place your product notifications send from?
- Two streams, one customer. A password reset and a re-engagement campaign want opposite things but reach the same person. Two vendors means two DNS setups, two reputations and two suppression lists that disagree with each other. One account has the opposite trap: an unsubscribe from the newsletter must not stop the password reset. Loops writes that rule into its transactional docs, where unsubscribed contacts still get every transactional email. Ask any service how its suppression list treats the two before you move.
- Your customers' domains. If your customers send under their own brand, you need a sending domain per customer, and one customer's complaint rate must not touch another's. Amazon added tenant management to SES for this case, so a software company sending for many customers keeps a separate reputation profile for each. In Nitrosend the unit is a brand, with its own sending domain, contacts and campaigns, and each exact sender keeps its own reputation and capacity, so one customer's sender cannot borrow another's trust.
- The price curve. Pricing by contacts hits SaaS hard, because a SaaS keeps every signup and mails an active fraction of them. Pricing by emails sent usually fits this shape better, and every plan on Nitrosend has unlimited contacts. Email marketing for SaaS covers the lifecycle side.
The setup decision most SaaS teams get wrong
Send product email and marketing email from different subdomains, on day one, before you have a reputation to protect. If notifications.yourapp.com carries password resets and mail.yourapp.com carries campaigns, a campaign that draws complaints cannot take the resets down with it. Teams that skip it because it is one more DNS record find out during their first big send. Some services build the split in: Customer.io only lets a domain into its transactional IP pool if it is a separate sending domain kept for transactional mail.
The split protects reputation, not your obligations. Gmail counts every message from the same primary domain, subdomains included, toward its line of about 5,000 a day for bulk senders, and a domain that crosses that line once is a bulk sender for good. A SaaS that emails 5,000 Gmail users in one day, with a launch announcement for example, is held to the bulk sender requirements on every subdomain after that, the one carrying password resets included: authenticated mail, no unwanted mail and an easy unsubscribe. Transactional email compared with marketing email covers the split, and the email authentication records are what each subdomain needs.
For customers who send under their own name, decide early whether they send as you or as themselves. Sending as you is simpler and means one reputation you control. Sending as them needs a verified domain per customer, and means a careless customer can hurt their own delivery but not everyone else's. The second is more work and is almost always right once you have real customers. Count the domains before you pick a plan. Nitrosend includes 1/3/5/10 sending domains on Free/Pro/Growth/Scale, with Enterprise on contract, with 3/5/10/unlimited brands on Free/Pro/Growth/Scale respectively. Resend includes 3 on Free and 10 on Pro, and sells 100 more for $20 a month because a domain per customer runs out quickly. Check each subdomain with a placement test before your first real campaign, and read what email deliverability is if the numbers surprise you.
Email API for SaaS FAQ
Nitrosend, with the top score in this review, 83.75 out of 100. Product email and lifecycle email run on separate streams in one account with unlimited contacts, an AI assistant can sign up and send product email from it without anyone opening a dashboard, campaigns and flows send only after approval, and it starts at $20 a month. Pick Loops for one flat price while your marketing list is small, Resend if product email is the whole job, and Postmark plus a separate marketing tool if product email reliability is the only thing that matters.
One account with the streams kept apart inside it is usually better than two vendors, because two vendors means two reputations and two suppression lists that drift apart. Whichever you choose, send the two from separate subdomains.
Verify a sending domain per customer so one customer's complaints cannot affect another's delivery. Check each service's limit on domains per account, because this is where they differ most: Nitrosend Starter includes 5 sending domains and 5 brands, with larger allowances on higher plans, and Resend includes 10 domains on Pro and sells 100 more for $20 a month. Bring your own sending keys covers the other route, sending through a provider account you already have.
By emails, in most cases, because a SaaS keeps every signup and mails a fraction of them. Pricing by contacts suits a small list mailed often. On this page Loops and Customer.io price by contacts, and Nitrosend, Resend, Brevo and Postmark by emails sent.
Nitrosend. It scores 9 out of 10 on working from your AI assistant, the test worth the most points on this page. Loops, Resend and Customer.io score 8, Amazon SES 7, Postmark 6 and Brevo 5. The gap is setup: an agent can sign up to Nitrosend over the API and send from a ready-made sender, while the others need a person to sign in, create a key or set up the account first.
Yes. Nitrosend, Resend, Loops, Customer.io and Brevo host MCP servers an assistant can connect to. Of the seven here, only Nitrosend lets the assistant create the account and get a ready sender without a person verifying a domain first, and its tools cover contacts, segments, flows and reporting as well as sending. Best email API for AI agents ranks the field on that job.
In Claude Code, run claude mcp add --transport http nitrosend https://api.nitrosend.com/mcp, then /mcp to sign in. In Claude Desktop or Claude.ai, connect Nitrosend from the connectors directory. Then ask in plain words, for example for a welcome flow for new signups. Brand Kit reads your site so the emails come out in your brand, and the flow sends only once it is approved. Your application sends password resets and receipts itself with POST /v1/my/messages and an Idempotency-Key header, so a retried request does not send the email twice.
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