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Point any SMTP client at the Brudcast relay to send from your verified domain. Use it when your software can’t call an HTTP API.
Before you start, you need your own verified sending domain. The Brudcast trial address has no SMTP credentials. See Email overview.

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Connection settings

If the SMTP Settings panel on your domain shows a different host name, use out-smtp.prod.brudcast.com.

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Choosing a port

  • 587 is the standard submission port. Start here.
  • 2525 works the same way. Use it when a network blocks 587.
  • 465 encrypts from the first byte. Use it when your client calls this “SSL” or “implicit TLS”.
  • 25 works, but many cloud providers and ISPs block outgoing traffic on it.
On 587, 2525 and 25 your client must send STARTTLS before it logs in. If it tries AUTH on an unencrypted connection, the relay replies 538 Error: Must issue a STARTTLS command first. That keeps your password from ever crossing the network in the clear.

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Get SMTP credentials

1

Open the domain

Go to Channels > Email, open the Domains tab and select your domain.
2

Add an SMTP user

Open the SMTP Credentials tab and select Add New SMTP User. Give it a name that says which application will use it.
3

Copy the credentials

Copy the username and password. The password is shown only once.
See SMTP users to regenerate a password or deactivate a user.

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Rules

  • The envelope sender must be on the SMTP user’s domain. Otherwise the relay rejects MAIL FROM with 550 MAIL FROM domain does not match authenticated domain. Use an address on the same domain in the From header too.
  • Messages can be up to 25 MB, including attachments.
  • A message must have a From header. Without one, the relay replies 550 Missing From address.
  • A missing subject becomes (no subject). A message with no text or HTML part is sent with an empty text body.

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What the relay doesn’t carry over

The relay doesn’t forward your message byte for byte. It reads the From, To and Cc headers, the subject, the text and HTML parts and the attachments, then builds a new message from those. Brudcast signs and tracks that new message. Anything else is lost:
  • Bcc recipients aren’t delivered. Recipients that appear only in the SMTP envelope (RCPT TO), and not in a To or Cc header, are dropped. This is how most libraries send Bcc.
  • Reply-To is dropped. Replies go to the From address.
  • Custom headers are dropped, including any List-Unsubscribe you set yourself.
If you need any of these, use the email send API. It accepts bcc, replyTo and custom headers.

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Limits

Your organization’s sending limits apply to SMTP the same as to the API. The relay counts them once per SMTP transaction, when your client sends MAIL FROM, whatever the number of recipients. Over a limit, the relay replies 451 Rate limit exceeded: <window>, for example 451 Rate limit exceeded: perMinute. 451 is temporary: your client or mail server queues the message and tries again later. See Rate limits.

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Replies you might see

See Errors for the full list.

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What happens next

The relay accepts the message as soon as it’s queued. Delivery to each recipient’s mail server happens next. SMTP gives you no job ID, so use the message log (filter by recipient) or webhooks to follow up.

Framework settings

Copy-paste configuration for Nodemailer, Laravel, Django, Rails, WordPress and PHPMailer.

Email send API

The HTTP alternative that keeps Bcc, Reply-To and headers.

SMTP users

Create, regenerate and deactivate SMTP credentials.