Configure Upstream SMTP

Configure Upstream SMTP

Relaywright relays accepted mail to one configured upstream smart host.

Open:

Settings -> Relay Settings

Listener Settings

Configure how devices connect to Relaywright:

• bind to all interfaces, or choose a specific local IP;
• SMTP listener TCP port;
• listener host name;
• maximum accepted message size;
• optional STARTTLS and certificate path.

STARTTLS certificate paths must point at certificate files supported by the app. If STARTTLS is enabled, configure a certificate path.

Upstream Settings

Configure the remote smart host:

• upstream host name or IP address;
• upstream TCP port;
• TLS mode;
• timeout in seconds;
• authentication mode.

Host fields should be hostnames or IP literals, not URLs or paths.

Authentication Modes

Relaywright supports:

• no upstream authentication;
• basic username/password authentication;
• Microsoft 365 OAuth client credentials.

For Microsoft 365 OAuth, configure:

• mailbox address;
• tenant ID or tenant domain;
• client ID;
• client secret.

The selected mailbox and Microsoft Entra app must have the required Exchange SMTP OAuth permissions outside Relaywright.

Delivery And Retention

Relay settings also control:

• delivery concurrency;
• maximum retry count;
• initial and maximum retry delays;
• message expiration;
• delivered, failed, and operational event retention.

SMTP listener changes restart the listener. Delivery changes wake the delivery worker so eligible queued work can move promptly.

Validation

After saving:

1. Run Diagnostics.
2. Send a test email through the configured upstream.
3. Confirm accepted messages appear in Queue Operations and later move to Delivered or a retry state.