> ## Documentation Index
> Fetch the complete documentation index at: https://docs.brudcast.com/llms.txt
> Use this file to discover all available pages before exploring further.
# SMTP users
> Create credentials for the Brudcast SMTP relay, connect your application, and regenerate or delete them safely.
export const Screenshot = ({id, src, srcDark, alt, caption}) => {
if (!src) {
return } />;
}
return
{caption && {caption}}
;
};
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](/developers/sending/http-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.
## Create an SMTP user
Go to **Channels > Email**, open the **Domains** tab, select the domain, then select the
**SMTP Credentials** tab.
Select **Add New SMTP User**. In **Description**, say where it will be used, for example
`Billing app, production`. The description is optional. Select **Create**.
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.
## Connection settings
| Setting | Value |
| -------------- | --------------------------------------------------------------------- |
| Host | `out-smtp.prod.brudcast.com` |
| Port | `465` with TLS from the start, or `587`, `2525` or `25` with STARTTLS |
| Authentication | `PLAIN` or `LOGIN` |
| Username | The SMTP username from the dialog |
| Password | The SMTP password from the dialog |
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](/developers/sending/smtp-relay).
## 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.
## 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.
## 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.
## SMTP or the send API
| | SMTP relay | Send API |
| ----------------------------- | ------------------------------------------ | ------------------------- |
| Integration effort | None if your app already sends mail | One HTTP call |
| Bcc, Reply-To, custom headers | Not supported | Supported |
| Maximum size | 25 MB per message | 10 MB request body |
| Feedback | SMTP reply codes | A `jobId` you can look up |
| Best for | Existing apps and frameworks with a mailer | New integrations |
## Related
Code samples and protocol details.
Credentials for the send API.
SMTP error replies explained.