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Supabase Step 1
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.

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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.

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SMTP Credentials

Use the following credentials to configure your SMTP client:
SettingValue
Hostsmtp.autosend.com
Port465, 587
Usernameautosend
PasswordAS_xxxx (Your AutoSend API key secret)
EncryptionTLS/SSL (see port guide below)

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Port Configuration

AutoSend supports multiple ports to accommodate different network configurations:
PortSecurityDescription
465Implicit TLSSMTPS - Connection is encrypted from the start. Recommended for most uses.
587STARTTLSSubmission 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.

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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>',
});

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Testing with Swaks

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

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Installation

brew install swaks

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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."

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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

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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.

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Platform Integrations

AutoSend SMTP works with any platform that supports SMTP configuration:

Auth0

Customer.io

Descope

Nodemailer

Supabase

WordPress

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Troubleshooting

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
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
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
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

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FAQs

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.
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.
Yes, AutoSend SMTP supports standard MIME attachments. Most SMTP libraries handle attachment encoding automatically. The maximum message size is 25MB including attachments.
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.
Yes! Webhooks are triggered for all events (delivery, bounce, open, click, etc.) regardless of whether the email was sent via SMTP or the API.
Yes, you can send from any email address on a verified domain. Simply use the desired sender address in the “From” field.

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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