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Documentation Index

Fetch the complete documentation index at: https://docs.paubox.com/llms.txt

Use this file to discover all available pages before exploring further.

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Why migrate

Resend does not sign Business Associate Agreements (BAAs). HIPAA requires a signed BAA with any vendor that handles Protected Health Information (PHI) in transit — including transactional email providers. Paubox is purpose-built for HIPAA-compliant email and signs a BAA with every customer, and TLS is always-on for every message. Resend’s API uses familiar Bearer-auth and JSON patterns, so the switch is a small refactor for developers already comfortable with Resend.

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What stays the same

  • REST API over HTTPS with JSON request bodies
  • API key authentication via the Authorization: Bearer header
  • Domain authentication: SPF and DKIM records required
  • SMTP as an alternative to the HTTP API
  • Webhook-based event notifications for delivery status

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Key differences

DimensionResendPaubox Email API
Base URLhttps://api.resend.com/emailshttps://api.paubox.net/v1/$PAUBOX_ENDPOINT/messages
Auth headerAuthorization: Bearer $RESEND_API_KEYAuthorization: Bearer $PAUBOX_API_KEY
Request body shapefrom, to, subject, html flat keysdata.message object with headers and content keys
Recipients fieldto — array of stringsrecipients — array of strings, nested under data.message
SMTP hostsmtp.resend.comsmtp.paubox.com
SMTP usernameresend (literal)apikey (literal)
SMTP port465 (recommended), 587, 25587 (also supports 465, 25)
Webhook eventsemail.sent, email.delivered, email.bounced, email.opened, email.clicked, email.complained, email.delivery_delayeddelivered, opened, temporary_failure, permanent_failure
Batch send/emails/batch endpoint/bulk_messages endpoint, recommended max 50 per request
TLS enforcementOptionalAlways-on, cannot be disabled
BAA availableNoYes — signed with every customer

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Send a single email

curl -X POST https://api.resend.com/emails \
  -H "Authorization: Bearer $RESEND_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "provider@yourclinic.com",
    "to": ["patient@example.com"],
    "subject": "Your appointment summary",
    "html": "<p>See attached.</p>"
  }'
Note:$PAUBOX_ENDPOINT is the username shown on your Paubox Email API > Settings page — not your email address.

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SMTP configuration

const transporter = nodemailer.createTransport({
  host: 'smtp.resend.com',
  port: 465,
  auth: {
    user: 'resend',
    pass: process.env.RESEND_API_KEY,
  },
});
Tip:Two changes are required: update host from smtp.resend.com to smtp.paubox.com, and change the literal username from resend to apikey.

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Webhook event mapping

Resend eventPaubox event keyNotes
email.deliveredapi_mail_log_delivered
email.openedapi_mail_log_opened
email.bouncedapi_mail_log_permanent_failure
email.delivery_delayedapi_mail_log_temporary_failure
email.clicked— no equivalentRemove handler or no-op; poll click data via Get message receipt
email.complained— no equivalentRemove handler
email.sent— no equivalentRemove handler; delivered confirms acceptance
Note:Click tracking is available by polling GET /message_receipt?sourceTrackingId=... — it is not delivered as a push webhook event.

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Migration checklist

1

Sign a BAA with Paubox

Required before go-live. Contact Paubox to initiate the Business Associate Agreement.
2

Create an account and verify your sending domain

Add your domain on the Paubox Email API > Settings page and complete the TXT record verification. See the Quickstart guide for step-by-step instructions.
3

Generate a Paubox API key

From the Settings page, generate an API key and note your customer endpoint (https://api.paubox.net/v1/YOUR_USERNAME).
4

Update base URL, auth header, and request body

Apply the changes shown in the Key differences table and Send a single email section above. Note that recipients move from a top-level to array into data.message.recipients.
5

Update SMTP credentials

If you use the SMTP path, update host to smtp.paubox.com and change the literal username from resend to apikey. See SMTP configuration above.
6

Remap or remove webhook handlers

Update your webhook endpoint using the event mapping table above. Remove handlers for email.clicked, email.complained, and email.sent.
7

Remove any code that disables TLS

Paubox enforces TLS on every message. Any allowNonTLS: true or equivalent settings should be removed.
8

Send a test message

Confirm delivery using the Get message receipt endpoint with the sourceTrackingId returned from your test send.
9

Swap DNS records

Replace Resend SPF/DKIM records with the Paubox records shown in your Settings page.
10

Revoke Resend API keys

Once traffic has fully moved to Paubox, revoke your Resend API keys.

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Next steps

Quickstart guide

Full setup walkthrough from account creation to first send

Webhooks reference

Configure delivery event notifications

Batch send

Send up to 50 messages in a single request

SMTP API

Connect via SMTP instead of REST