Reliable Email Infrastructure

Fast, secure email API
for transaction and marketing emails

A powerful and reliable email sending API for businesses. Deliver transactional, marketing, and notification emails at scale — with world-class deliverability and simple integrations.

Start Free View API docs

Fast setup
First email in minutes
High deliverability
Built for the inbox
Built to scale
From launch to growth

1,000+Emails per secondBuilt to scale

curl --request POST "https://api.sendmero.com/v1/messages" \
  --header "Authorization: Bearer $SENDMERO_API_KEY" \
  --header "Content-Type: application/json" \
  --data '{
    "from": "onboarding@yourapp.com",
    "to": "user@example.com",
    "subject": "Your verification code",
    "html": "<p>Your code is 482913</p>"
  }'

99%+Delivery rate

< 1 secondMedian delivery time

Global infrastructureSend worldwide

Built for the tools you already use

Node.js
Python
PHP
Ruby
Go
Java
.NET
Elixir

Integrate in 30 mins

A simple, elegant interface so you can start sending emails in minutes. It fits right into your code for your favorite programming languages.

curl --request POST "https://api.sendmero.com/v1/messages" \
  --header "Authorization: Bearer $SENDMERO_API_KEY" \
  --header "Content-Type: application/json" \
  --data '{
    "from": "onboarding@yourapp.com",
    "to": "user@example.com",
    "subject": "Your verification code",
    "html": "<p>Your code is 482913</p>"
  }'

curl --url "smtp://$SMTP_HOST:$SMTP_PORT" \
  --ssl-reqd \
  --user "$SMTP_USERNAME:$SMTP_PASSWORD" \
  --mail-from "onboarding@yourapp.com" \
  --mail-rcpt "user@example.com" \
  --crlf --upload-file - <<'EMAIL'
From: onboarding@yourapp.com
To: user@example.com
Subject: Your verification code
MIME-Version: 1.0
Content-Type: text/html; charset=UTF-8

<p>Your code is 482913</p>
EMAIL

const response = await fetch("https://api.sendmero.com/v1/messages", {
  method: "POST",
  headers: {
    Authorization: "Bearer " + process.env.SENDMERO_API_KEY,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    from: "onboarding@yourapp.com",
    to: "user@example.com",
    subject: "Your verification code",
    html: "<p>Your code is 482913</p>",
  }),
});

console.log(response.status, await response.json());

Setupnpm install nodemailer · save as send.mjs

import nodemailer from "nodemailer";

const smtp = nodemailer.createTransport({
  host: process.env.SMTP_HOST,
  port: Number(process.env.SMTP_PORT),
  secure: false,
  requireTLS: true,
  auth: {
    user: process.env.SMTP_USERNAME,
    pass: process.env.SMTP_PASSWORD,
  },
});

const result = await smtp.sendMail({
  from: "onboarding@yourapp.com",
  to: "user@example.com",
  subject: "Your verification code",
  html: "<p>Your code is 482913</p>",
});
console.log(result.messageId);

import json, os
from urllib.request import Request, urlopen

message = {
    "from": "onboarding@yourapp.com",
    "to": "user@example.com",
    "subject": "Your verification code",
    "html": "<p>Your code is 482913</p>",
}
request = Request(
    "https://api.sendmero.com/v1/messages",
    data=json.dumps(message).encode(),
    headers={
        "Authorization": "Bearer " + os.environ["SENDMERO_API_KEY"],
        "Content-Type": "application/json",
    },
    method="POST",
)
with urlopen(request) as response:
    print(response.status, json.load(response))

import os, smtplib, ssl
from email.message import EmailMessage

message = EmailMessage()
message["From"] = "onboarding@yourapp.com"
message["To"] = "user@example.com"
message["Subject"] = "Your verification code"
message.set_content("<p>Your code is 482913</p>", subtype="html")

with smtplib.SMTP(
    os.environ["SMTP_HOST"], int(os.environ["SMTP_PORT"]), timeout=30
) as smtp:
    smtp.starttls(context=ssl.create_default_context())
    smtp.ehlo()
    smtp.login(os.environ["SMTP_USERNAME"], os.environ["SMTP_PASSWORD"])
    smtp.send_message(message)

<?php
$request = curl_init('https://api.sendmero.com/v1/messages');
curl_setopt_array($request, [
    CURLOPT_POST => true,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        'Authorization: Bearer ' . getenv('SENDMERO_API_KEY'),
        'Content-Type: application/json',
    ],
    CURLOPT_POSTFIELDS => json_encode([
        'from' => 'onboarding@yourapp.com',
        'to' => 'user@example.com',
        'subject' => 'Your verification code',
        'html' => '<p>Your code is 482913</p>',
    ]),
]);
$response = curl_exec($request);
if ($response === false) throw new RuntimeException(curl_error($request));
echo $response;
curl_close($request);

Setupcomposer require phpmailer/phpmailer

<?php
use PHPMailer\PHPMailer\PHPMailer;
require 'vendor/autoload.php';

$mail = new PHPMailer(true);
$mail->isSMTP();
$mail->Host = getenv('SMTP_HOST');
$mail->Port = (int) getenv('SMTP_PORT');
$mail->SMTPAuth = true;
$mail->Username = getenv('SMTP_USERNAME');
$mail->Password = getenv('SMTP_PASSWORD');
$mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;

$mail->setFrom('onboarding@yourapp.com');
$mail->addAddress('user@example.com');
$mail->Subject = 'Your verification code';
$mail->isHTML(true);
$mail->Body = '<p>Your code is 482913</p>';
$mail->send();

require "net/http"
require "json"

uri = URI("https://api.sendmero.com/v1/messages")
request = Net::HTTP::Post.new(uri)
request["Authorization"] = "Bearer " + ENV.fetch("SENDMERO_API_KEY")
request["Content-Type"] = "application/json"
request.body = {
  from: "onboarding@yourapp.com",
  to: "user@example.com",
  subject: "Your verification code",
  html: "<p>Your code is 482913</p>"
}.to_json

response = Net::HTTP.start(uri.host, uri.port, use_ssl: true) do |http|
  http.request(request)
end
puts response.code, response.body

Setupgem install net-smtp

require "net/smtp"

message = <<~EMAIL
  From: onboarding@yourapp.com
  To: user@example.com
  Subject: Your verification code
  MIME-Version: 1.0
  Content-Type: text/html; charset=UTF-8

  <p>Your code is 482913</p>
EMAIL

smtp = Net::SMTP.new(ENV.fetch("SMTP_HOST"), Integer(ENV.fetch("SMTP_PORT")))
smtp.enable_starttls
smtp.start(
  helo: "yourapp.com",
  user: ENV.fetch("SMTP_USERNAME"),
  secret: ENV.fetch("SMTP_PASSWORD"),
  authtype: :plain
) do |connection|
  connection.send_message(message, "onboarding@yourapp.com", "user@example.com")
end

package main

import (
    "io"
    "net/http"
    "os"
    "strings"
)

func main() {
    body := strings.NewReader(`{
        "from": "onboarding@yourapp.com",
        "to": "user@example.com",
        "subject": "Your verification code",
        "html": "<p>Your code is 482913</p>"
    }`)
    request, err := http.NewRequest("POST", "https://api.sendmero.com/v1/messages", body)
    if err != nil { panic(err) }
    request.Header.Set("Authorization", "Bearer "+os.Getenv("SENDMERO_API_KEY"))
    request.Header.Set("Content-Type", "application/json")
    response, err := http.DefaultClient.Do(request)
    if err != nil { panic(err) }
    defer response.Body.Close()
    io.Copy(os.Stdout, response.Body)
}

Setupgo get github.com/wneessen/go-mail

package main

import (
    "os"
    "strconv"
    mail "github.com/wneessen/go-mail"
)

func main() {
    port, err := strconv.Atoi(os.Getenv("SMTP_PORT"))
    if err != nil { panic(err) }
    smtp, err := mail.NewClient(os.Getenv("SMTP_HOST"),
        mail.WithPort(port),
        mail.WithTLSPolicy(mail.TLSMandatory),
        mail.WithSMTPAuth(mail.SMTPAuthPlain),
        mail.WithUsername(os.Getenv("SMTP_USERNAME")),
        mail.WithPassword(os.Getenv("SMTP_PASSWORD")),
    )
    if err != nil { panic(err) }

    message := mail.NewMsg()
    if err := message.From("onboarding@yourapp.com"); err != nil { panic(err) }
    if err := message.To("user@example.com"); err != nil { panic(err) }
    message.Subject("Your verification code")
    message.SetBodyString(mail.TypeTextHTML, "<p>Your code is 482913</p>")
    if err := smtp.DialAndSend(message); err != nil { panic(err) }
}

import java.net.URI;
import java.net.http.*;

class SendEmail {
  public static void main(String[] args) throws Exception {
    String message = """
        {
          "from": "onboarding@yourapp.com",
          "to": "user@example.com",
          "subject": "Your verification code",
          "html": "<p>Your code is 482913</p>"
        }
        """;
    var request = HttpRequest.newBuilder()
        .uri(URI.create("https://api.sendmero.com/v1/messages"))
        .header("Authorization", "Bearer " + System.getenv("SENDMERO_API_KEY"))
        .header("Content-Type", "application/json")
        .POST(HttpRequest.BodyPublishers.ofString(message)).build();
    var response = HttpClient.newHttpClient()
        .send(request, HttpResponse.BodyHandlers.ofString());
    System.out.println(response.body());
  }
}

SetupMaven: org.eclipse.angus:jakarta.mail:2.0.4

import jakarta.mail.*;
import jakarta.mail.internet.*;
import java.util.Properties;

class SendEmail {
  public static void main(String[] args) throws Exception {
    var properties = new Properties();
    properties.setProperty("mail.smtp.host", System.getenv("SMTP_HOST"));
    properties.setProperty("mail.smtp.port", System.getenv("SMTP_PORT"));
    properties.setProperty("mail.smtp.auth", "true");
    properties.setProperty("mail.smtp.starttls.enable", "true");
    properties.setProperty("mail.smtp.starttls.required", "true");
    properties.setProperty("mail.smtp.ssl.checkserveridentity", "true");

    var message = new MimeMessage(Session.getInstance(properties));
    message.setFrom(new InternetAddress("onboarding@yourapp.com"));
    message.setRecipients(Message.RecipientType.TO, "user@example.com");
    message.setSubject("Your verification code");
    message.setContent("<p>Your code is 482913</p>", "text/html; charset=UTF-8");

    Transport.send(message, System.getenv("SMTP_USERNAME"),
        System.getenv("SMTP_PASSWORD"));
  }
}

using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Net.Http.Json;

using var client = new HttpClient();
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue(
    "Bearer", Environment.GetEnvironmentVariable("SENDMERO_API_KEY"));

using var response = await client.PostAsJsonAsync(
    "https://api.sendmero.com/v1/messages",
    new {
        from = "onboarding@yourapp.com",
        to = "user@example.com",
        subject = "Your verification code",
        html = "<p>Your code is 482913</p>"
    });

Console.WriteLine(await response.Content.ReadAsStringAsync());

Setupdotnet add package MailKit

using System;
using MailKit.Net.Smtp;
using MailKit.Security;
using MimeKit;

var message = new MimeMessage();
message.From.Add(MailboxAddress.Parse("onboarding@yourapp.com"));
message.To.Add(MailboxAddress.Parse("user@example.com"));
message.Subject = "Your verification code";
message.Body = new TextPart("html") { Text = "<p>Your code is 482913</p>" };

using var smtp = new SmtpClient();
await smtp.ConnectAsync(
    Environment.GetEnvironmentVariable("SMTP_HOST"),
    int.Parse(Environment.GetEnvironmentVariable("SMTP_PORT")!),
    SecureSocketOptions.StartTls);
await smtp.AuthenticateAsync(
    Environment.GetEnvironmentVariable("SMTP_USERNAME"),
    Environment.GetEnvironmentVariable("SMTP_PASSWORD"));
await smtp.SendAsync(message);
await smtp.DisconnectAsync(true);

:inets.start()
:ssl.start()

url = String.to_charlist("https://api.sendmero.com/v1/messages")
token = String.to_charlist("Bearer " <> System.fetch_env!("SENDMERO_API_KEY"))
body = ~s({
  "from": "onboarding@yourapp.com",
  "to": "user@example.com",
  "subject": "Your verification code",
  "html": "<p>Your code is 482913</p>"
})

{:ok, {{_, status, _}, _, response}} = :httpc.request(
  :post, {url, [{~c"authorization", token}], ~c"application/json", body},
  [ssl: [verify: :verify_peer, cacerts: :public_key.cacerts_get()]],
  [body_format: :binary]
)
IO.inspect({status, response})

Setupmix.exs: {:gen_smtp, "~> 1.3"} · mix deps.get · Erlang/OTP 25+

{:ok, _} = Application.ensure_all_started(:gen_smtp)
host = System.fetch_env!("SMTP_HOST") |> String.to_charlist()

message = Enum.join([
  "From: onboarding@yourapp.com",
  "To: user@example.com",
  "Subject: Your verification code",
  "MIME-Version: 1.0",
  "Content-Type: text/html; charset=UTF-8",
  "",
  "<p>Your code is 482913</p>",
  ""
], "\r\n")

result = :gen_smtp_client.send_blocking(
  {"onboarding@yourapp.com", ["user@example.com"], message},
  relay: host,
  port: System.fetch_env!("SMTP_PORT") |> String.to_integer(),
  username: System.fetch_env!("SMTP_USERNAME"),
  password: System.fetch_env!("SMTP_PASSWORD"),
  no_mx_lookups: true,
  tls: :always,
  auth: :always,
  tls_options: [
    verify: :verify_peer,
    cacerts: :public_key.cacerts_get(),
    server_name_indication: host,
    depth: 10,
    customize_hostname_check: [
      match_fun: :public_key.pkix_verify_hostname_match_fun(:https)
    ]
  ]
)
IO.inspect(result)

Set SENDMERO_API_KEY to your API key.

Set SMTP_HOST, SMTP_PORT, SMTP_USERNAME, and SMTP_PASSWORD using your dashboard credentials. These examples use STARTTLS.

Proactive Inbox Placement

See whether you are landing in the inbox, promotions, or spam before your users do — and catch ISP-specific issues before they spread.

Real-Time Message Logs

Every send is tracked from Queued to Delivered to Opened, with human-readable error codes the moment something bounces or fails.

Hybrid REST API & SMTP

Integrate deeply with a modern REST API, or drop in SMTP credentials for legacy systems in minutes. Same deliverability, either way.

Global Scale Infrastructure

Built to absorb traffic spikes — flash sales, security alerts, OTP storms — without added latency or dropped sends.

Domain Authentication & Security

Guided setup for SPF, DKIM, and DMARC, plus IP allowlisting and role-based access so developers and marketers get exactly the access they need.

Modular Webhooks

Get a real-time POST to your server the instant an email is delivered, opened, clicked, bounced, or marked as spam.

Deliverability

Reach humans, not spam folders

Every domain gets guided SPF, DKIM, and DMARC setup, proactive blocklist monitoring, and inbox placement tracking — so you find out about a reputation problem before your users do.

Dedicated IPs that auto warm up, no waiting period
Dynamic suppression lists for bounces and complaints
DNS monitoring with alerts on any change or regression

Your email Their inbox Made for
the inbox

Gmail
Yahoo
Outlook

Your brand, recognized

A verified identity and your logo in supported inboxes.
Reputation protected

Spot blocklist, domain, and impersonation issues early.
Healthier contact lists

Honor opt-outs and suppress bounces and complaints.
Faster delivery at scale

Automatic IP warm-up and delivery closer to your audience.

Email analytics

Track what happens to every email

See which emails reach your audience and how people engage. Track opens and clicks, catch delivery issues, and use past results to improve your next campaign.

Measure engagement with real-time open and click tracking
Spot bounces and failed deliveries with clear explanations
Review past performance and export reports to plan your next campaign

Your campaign Their response

Delivered Delivery confirmed
Opened Open recorded
Clicked Link activity

Bounce flagged

Follow opens

See when opens are recorded for your campaigns.
Track clicks

Follow link activity as your audience engages.
Catch delivery issues

Find bounces and failed sends with clear explanations.
Make the next send better

Compare past performance and export your reports.

Security & reputation

Protect the trust behind every send

Your audience knows your brand. Help them trust every email from it with a verified sending domain, protected account access, and the right permissions for everyone on your team.

Authenticate your domain with guided SPF, DKIM, and DMARC setup
Restrict API and SMTP access to approved server IP addresses
Give marketers template access and developers API access with team roles

Your identity Your team Access
by role

Marketing Templates
Developers API & SMTP

Protect your identity

Authenticate your domain with SPF, DKIM, and DMARC.
Send from trusted IPs

Allowlist IPs for your API and SMTP connections.
Give each team the right access

Set roles for templates and developer access.
Watch your reputation

Monitor sender reputation and spot issues early.

Live Analytics

Delivery, opens, clicks, and bounces in real time — filterable by domain, tag, or template.

REST API & SMTP

One account, two integration paths. Use whichever fits the system you're sending from.

Responsive Support

Real engineers answer, with sub-4-hour response times during business hours.

Enterprise-Grade Security

SOC 2-track infrastructure with encryption in transit and at rest, and granular role-based access.

Start with a hello

~1s

Median transactional delivery

Go big on launch day

1,000+/sec

Emails processed per second

Keep customers in the loop

99%+

Transactional delivery rate

Share your next big idea

98%+

Marketing delivery rate

Start free. Grow from there.

Find the right plan for your next campaign and every send after it.

View pricing

Migration & scale

4M+ emails per month

“We swapped our old SMTP relay for SendMero in an afternoon. The webhooks alone saved us a full sprint of building our own bounce-handling logic.”

Priya Nandan Backend Lead, Loopline

Inbox visibility

99.4% inbox rate

“Inbox placement tracking caught a DKIM misconfiguration before it hurt our sender reputation. That single alert probably saved our deliverability.”

Marcus Webb CTO, Fenwick Labs

A faster first send

12 min to first send

“Docs were good enough that I never had to open a support ticket. Copy, paste, verify a domain, and OTPs were landing in inboxes.”

Alina Roth Founding Engineer, Ledgerly

SendMero is built API-first for developers: a single endpoint for both transactional and marketing sends, message-level logs, and webhooks for every event. You get the deliverability tooling of a dedicated ESP without the campaign-builder overhead you don't need.

Yes. Every account gets REST API credentials and SMTP credentials on the same domain reputation, so legacy systems that only speak SMTP get the same deliverability as an app calling the API directly.

Nothing is blocked. Overage on paid plans is billed per additional 1,000 emails at the rate shown on your plan, and you can set a soft spending cap in the dashboard as a guardrail against runaway sends.

Median transactional delivery time is under a second from API call to accepted-by-receiver, with infrastructure that sustains over 1,000 emails per second per account during bursts like OTP storms or flash sales.

Yes — and you should. We walk you through SPF, DKIM, and DMARC setup for your own domain so mail is authenticated as coming from you, not a shared SendMero subdomain.

Get Started Today

Start sending emails in minutes

Create an account, verify a domain, and send your first email — no sales call required.

Start Free Read the Docs Talk to Sales

Fast, secure email API
for transaction and marketing emails

Integrate in 30 mins

The granular control serious senders need

Proactive Inbox Placement

Real-Time Message Logs

Hybrid REST API & SMTP

Global Scale Infrastructure

Domain Authentication & Security

Modular Webhooks

Reach humans, not spam folders

Your brand, recognized

Reputation protected

Healthier contact lists

Faster delivery at scale

Track what happens to every email

Follow opens

Track clicks

Catch delivery issues

Make the next send better

Protect the trust behind every send

Protect your identity

Send from trusted IPs

Give each team the right access

Watch your reputation

Live Analytics

REST API & SMTP

Responsive Support

Enterprise-Grade Security

For the moments
you hit send.

Start with a hello

Go big on launch day

Keep customers in the loop

Share your next big idea

Start free. Grow from there.

For the teams
behind every send.

Common questions

Start sending emails in minutes

Fast, secure email APIfor transaction and marketing emails

Integrate in 30 mins

The granular control serious senders need

Proactive Inbox Placement

Real-Time Message Logs

Hybrid REST API & SMTP

Global Scale Infrastructure

Domain Authentication & Security

Modular Webhooks

Reach humans, not spam folders

Your brand, recognized

Reputation protected

Healthier contact lists

Faster delivery at scale

Track what happens to every email

Follow opens

Track clicks

Catch delivery issues

Make the next send better

Protect the trust behind every send

Protect your identity

Send from trusted IPs

Give each team the right access

Watch your reputation

Live Analytics

REST API & SMTP

Responsive Support

Enterprise-Grade Security

Start with a hello

Go big on launch day

Keep customers in the loop

Share your next big idea

Start free. Grow from there.

Common questions

Start sending emails in minutes

Fast, secure email API
for transaction and marketing emails