Testing and verifying your relay delivery

After setting up your relay, you’ll want to verify everything works before relying on it for production email. This guide walks you through a simple test process and covers the most common issues you might run into.

Step 1: Verify your domain

Before testing relay delivery, make sure your domain is fully verified in Cleanbox.

1. Go to Domains and click your domain.
2. Check the verification status — your MX, TXT, and SPF records should all show green checkmarks.
3. If any record shows a red X, fix your DNS configuration first. Relay delivery won’t work reliably until all records are verified.

Step 2: Check your relay configuration

1. Go to Relay and click your relay address.
2. Verify that the SMTP destination is correct — double-check the host, port, and TLS settings.
3. Make sure the relay address is set to Active.

Step 3: Send a test email

1. From an external email account (Gmail, Outlook, or any other provider), send a test message to your relay address.
2. Wait a minute, then check your destination mail server — the message should arrive in the inbox.
3. Also check the Messages page in Cleanbox. You should see the test message with the status “Delivered”.

Step 4: Check the spam report

Once your test message appears in Cleanbox, click the preview button to review the spam report.

• Check that authentication is passing — look for SPF and DKIM results.
• A clean test message should have a low spam score, close to 0.
• If any rules triggered, the report will show exactly which ones and why.

Step 5: Configure the validation token

This step is optional but recommended. Cleanbox adds a validation header to every relayed message. You can configure your mail server to check for this header and reject messages that bypass Cleanbox entirely. See the Relay token configuration article for setup instructions.

Common issues and fixes

Message shows in Cleanbox but not in your inbox

Check that your mail server accepts connections from Cleanbox. Verify the SMTP host and port are correct in your relay settings. Also check if your server has firewall rules that might block the connection.

Message is rejected or bounced

Check the message status in Cleanbox — the error details will indicate why delivery failed. Common causes include wrong credentials, an unreachable server, or a full mailbox.

High spam score on a legitimate test email

This is normal if the test message was very short or came from a free email provider. Check which rules triggered in the spam report — short messages and freemail senders often pick up a few points.

“via srs.cleanbox.to” in the email

This is expected. Cleanbox uses SRS (Sender Rewriting Scheme) when forwarding, which rewrites the envelope sender to preserve SPF alignment. The original sender information is preserved in the email headers, so replies still go to the right place.

Once everything checks out

Your relay is live and protecting your domain. For the first few days, we recommend:

• Monitoring the Messages page to make sure delivery is working as expected.
• Checking quarantine regularly in case legitimate messages are being caught.
• Adjusting your shield rules if needed based on what you see in the spam reports.

If you run into any issues that aren’t covered here, reach out to our support team and we’ll help you troubleshoot.