Send through the SMTP relay

Many tools can send email but cannot call an API: WordPress and WooCommerce, accounting and POS software, a website contact form, a scanner. Point them at Ha Tang's SMTP relay and their email goes out from your verified domain, with the same delivery, tracking and logs as everything else you send. Each message appears under Email → Emails with its status.

Before you start

• A verified sending domain. The relay only accepts a sender address on a domain verified in your business. See Add and verify a sending domain.
• An API key with the Send permission. It is your SMTP password. Creating keys needs the Developer access in the business; see API keys.

Connection settings

The same host, port, username and Encryption (STARTTLS) are listed under Email → Email settings → Connection details, with a ready-to-copy block of settings. In code, STARTTLS means secure: false (SMTP_SECURE=false): the connection is still encrypted, it just starts in plain text.

The relay refuses to log in until the connection is encrypted, so your API key never crosses the network in clear text.

Create the key

1. Open Email → API Keys and click Create key.
2. Name it after the app that will use it, for example WordPress shop.
3. Under What this key can do, tick Send for Email and nothing else. A key that can only send cannot read your contacts or change your domains if it leaks.
4. Optionally limit Sending domain to the one domain this app sends from.
5. Click Create key and copy the key at once: it is never shown again.

Give each app its own key, so you can revoke one without touching the others.

WordPress with WP Mail SMTP

1. Install the WP Mail SMTP plugin and open WP Mail SMTP → Settings.

2. Set From Email to an address on your verified domain, for example [email protected], and turn on Force From Email.

3. Under Mailer, choose Other SMTP.

4. Fill in:

   Field	Value
   SMTP Host	smtp.hatang.dev
   Encryption	TLS (this is STARTTLS in WP Mail SMTP)
   SMTP Port	5870
   Auto TLS	On
   Authentication	On
   SMTP Username	hatang
   SMTP Password	Your API key

5. Save, then send a test from WP Mail SMTP → Tools → Email Test.

The test appears under Email → Emails a few seconds later. WooCommerce order emails then go through Ha Tang too.

Other apps

Look for the "SMTP", "outgoing mail" or "mail server" settings and enter the values from the table above. Things to check:

• Sender address: always an address on your verified domain. Apps that send from wordpress@yourhost or root@localhost are refused until you change it.
• Encryption: STARTTLS or "TLS", never SSL.
• To: put at least one address in the To field. If a message only has Bcc recipients, Ha Tang moves the first one into To, where the others can see it.

Developers will find ready-made settings for Laravel, Django, Rails, Spring Boot, Nodemailer, PHPMailer and Postfix in the SMTP guide of the developer hub.

Limits

When it does not work

Every message the relay accepts is listed under Email → Emails with the source SMTP. If a message is missing there, the app never reached Ha Tang: check its own logs for one of the replies above.