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Create a username and password your application can use to send mail through the Brudcast SMTP relay. An SMTP user belongs to one sending domain. Use one when your application already sends mail over SMTP and you’d rather not rewrite it against the send API.
Before you start: you need a sending domain of your own. SMTP isn’t available on the managed sending address. Verify the domain before you send, or receiving servers can’t authenticate your mail.

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Create an SMTP user

1

Open the domain's SMTP Credentials tab

Go to Channels > Email, open the Domains tab, select the domain, then select the SMTP Credentials tab.
2

Add a user

Select Add New SMTP User. In Description, say where it will be used, for example Billing app, production. The description is optional. Select Create.
3

Copy the username and password

The SMTP User Created dialog shows the SMTP Username and SMTP Password. The password is shown once. Copy both into your application’s secret store, then select Done.
The new user shows Provisioning for a few seconds, then Active. Failed means it couldn’t be set up. Delete it and create another. Brudcast generates the username. It looks like an email address on your domain, for example 3f9a1c7e@mail.example.com, but it isn’t a mailbox. Use it exactly as shown. The password is 32 characters long.

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Connection settings

On ports 587, 2525 and 25, your client must send STARTTLS before it logs in. If it tries to log in first, it gets 538 Must issue a STARTTLS command first. Use port 2525 if your network blocks 587. Worked examples per language are in SMTP relay.

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Rules and limits

  • The from domain must match. The MAIL FROM address must be on the SMTP user’s domain. A user on mail.example.com can’t send as hello@other.example.com.
  • 25 MB per message, attachments included.
  • A message without a subject goes out as (no subject).
  • The relay rebuilds your message from its From, To, Cc, subject, text, HTML and attachments. That means:
    • Recipients given only in the SMTP envelope (Bcc) don’t receive the message. Put every recipient in To or Cc, or use the send API, which supports bcc.
    • Reply-To and custom headers are dropped. Use the send API if you need them.
  • Rate limits count once per SMTP transaction, however many recipients it has.
  • One user per application. You can then revoke one application’s access without an outage everywhere else.

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Regenerate a password

On the user’s row, open the More actions menu (the three-dot icon) and select Regenerate Password, then Regenerate. The Password Regenerated dialog shows the new password once. The old password stops working as soon as the new one is active, so update your application straight away.

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Delete a user

On the user’s row, open the More actions menu (the three-dot icon) and select Delete. Anything still using those credentials fails on its next connection. Check where the user is deployed before you remove it.

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SMTP or the send API

SMTP relay

Code samples and protocol details.

Sending keys

Credentials for the send API.

Email troubleshooting

SMTP error replies explained.