How to send email with AutoSend SMTP

AutoSend provides an SMTP relay service that allows you to send transactional emails using standard SMTP protocols. This is useful when integrating with platforms that require SMTP credentials, such as Supabase, WordPress, or other services that don’t support REST APIs.

Prerequisites

Verified Domain

Make sure you have a verified domain added in AutoSend to send emails from.

API Key

Create a new API key for SMTP authentication or use the existing one.

SMTP Credentials

Use the following credentials to configure your SMTP client:

Setting	Value
Host	`smtp.autosend.com`
Port	`465`, `587`
Username	autosend
Password	AS_xxxx (Your AutoSend API key secret)
Encryption	TLS/SSL (see port guide below)

Port Configuration

AutoSend supports multiple ports to accommodate different network configurations:

Port	Security	Description
`465`	Implicit TLS	SMTPS - Connection is encrypted from the start. Recommended for most uses.
`587`	STARTTLS	Submission port - Starts unencrypted, upgrades to TLS. Most widely supported.

Which port should I use? Start with port 587 (STARTTLS) as it’s the most widely supported. For implicit TLS, use port 465.

Integration Examples

const nodemailer = require('nodemailer');

const transporter = nodemailer.createTransport({
	host: 'smtp.autosend.com',
	port: 587,
	secure: true,
	auth: {
		user: 'autosend',
		pass: 'AS_xxx',
	},
});

await transporter.sendMail({
	from: '[email protected]',
	to: '[email protected]',
	subject: 'Hello from AutoSend',
	html: '<h1>Welcome!</h1><p>This email was sent via SMTP.</p>',
});

Platform Integrations

AutoSend SMTP works with any platform that supports SMTP configuration:

Auth0

Send authentication emails through AutoSend SMTP.

Customer.io

Send emails from Customer.io through AutoSend SMTP.

Descope

Send authentication emails from Descope through AutoSend SMTP.

Nodemailer

Send emails from Node.js apps using Nodemailer with AutoSend SMTP.

Supabase

Send auth emails from Supabase through AutoSend SMTP.

WordPress

Configure WordPress to send emails through AutoSend SMTP.

Testing with Swaks

Swaks (Swiss Army Knife for SMTP) is a powerful command-line tool for testing SMTP configurations.

Installation

brew install swaks

Basic Test

swaks --to [email protected] \
      --from [email protected] \
      --server smtp.autosend.com \
      --port 587 \
      --tls \
      --auth-user [email protected] \
      --auth-password AS_xxx
      --header "Subject: Test Email via SMTP" \
      --body "This email was sent via AutoSend SMTP."

Test with Implicit TLS (Port 465)

swaks --to [email protected] \
      --from [email protected] \
      --server smtp.autosend.com \
      --port 465 \
      --auth-user [email protected] \
      --auth-password as_your_api_key_here \
      --tlsc

Test with HTML Body

swaks --to [email protected] \
      --from [email protected] \
      --server smtp.autosend.com \
      --port 587 \
      --auth-user [email protected] \
      --auth-password as_your_api_key_here \
      --header "Content-Type: text/html" \
      --body "<h1>Test Email</h1><p>This is a test from swaks.</p>"

Add -v or -vv for detailed SMTP conversation logs.

Troubleshooting

Connection refused or timeout

Possible causes:

The SMTP port may be blocked by your firewall or ISP
Incorrect server hostname
Network connectivity issues

Solutions:

Verify the hostname is smtp.autosend.com
Check your firewall rules
Test connectivity: telnet smtp.autosend.com 587

Authentication failed

Possible causes:

Invalid API key
Username doesn’t match a verified sender

Solutions:

Verify your API key in the Dashboard
Ensure the username is a verified sender email address
Check that your domain is properly verified
Check for any extra whitespace in your credentials

TLS/SSL errors

Possible causes:

Using wrong encryption mode for the port
TLS certificate verification issues

Solutions:

For ports 465: Use implicit TLS (connection encrypted from start)
For ports 587: Use STARTTLS (starts unencrypted, upgrades to TLS)
If using swaks, add --tlsc flag only for ports 465

Emails not delivered

Possible causes:

Domain not verified
SPF/DKIM not configured
Recipient server blocking

Solutions:

Verify your sending domain is configured and verified in AutoSend
Check the sender email matches your verified domain
Add the required DNS records for SPF and DKIM
Review email activity in the Email Activity dashboard

FAQs

Can I see emails sent via SMTP in my dashboard?

Yes! All emails sent through SMTP appear in your AutoSend Dashboard under the Email Activity section. You can view delivery status, opens, clicks, and bounces just like API-sent emails.

What are the rate limits for SMTP?

SMTP rate limits are the same as the REST API. Your plan’s sending limits apply across both SMTP and API. Check your Dashboard for your current limits.

Can I send attachments via SMTP?

Yes, AutoSend SMTP supports standard MIME attachments. Most SMTP libraries handle attachment encoding automatically. The maximum message size is 25MB including attachments.

Is SMTP as fast as the API?

SMTP adds minimal overhead compared to the REST API. For high-volume sending or when you need immediate delivery confirmation, the API may be slightly faster. For most use cases, SMTP performance is excellent.

Do webhooks work with SMTP emails?

Yes! Webhooks are triggered for all events (delivery, bounce, open, click, etc.) regardless of whether the email was sent via SMTP or the API.

Can I use multiple sender addresses?

Yes, you can send from any email address on a verified domain. Simply use the desired sender address in the “From” field. But make sure the domain is verified in your AutoSend account.

Next Steps

Verify Your Domain

Set up SPF, DKIM, and DMARC for better deliverability

API Integration

Explore our REST API for more advanced use cases

Webhooks

Set up webhooks to track email events in real-time

Email Activity

Monitor your email delivery and engagement

Getting Started

Quickstart

Transactional Emails

Marketing Emails

Email Automations

Others

Prerequisites

Verified Domain

API Key

SMTP Credentials

Port Configuration

Integration Examples

Platform Integrations

Auth0

Customer.io

Descope

Nodemailer

Supabase

WordPress

Testing with Swaks

Installation

Basic Test

Test with Implicit TLS (Port 465)

Test with HTML Body

Troubleshooting

FAQs

Next Steps

Verify Your Domain

API Integration

Webhooks

Email Activity

Getting Started

Quickstart

Transactional Emails

Marketing Emails

Email Automations

Others

​Prerequisites

Verified Domain

API Key

​SMTP Credentials

​Port Configuration

​Integration Examples

​Platform Integrations

Auth0

Customer.io

Descope

Nodemailer

Supabase

WordPress

​Testing with Swaks

​Installation

​Basic Test

​Test with Implicit TLS (Port 465)

​Test with HTML Body

​Troubleshooting

​FAQs

​Next Steps

Verify Your Domain

API Integration

Webhooks

Email Activity

Prerequisites

SMTP Credentials

Port Configuration

Integration Examples

Platform Integrations

Testing with Swaks

Installation

Basic Test

Test with Implicit TLS (Port 465)

Test with HTML Body

Troubleshooting

FAQs

Next Steps