> This page is part of the [Customer.io documentation](https://docs.customer.io). For the complete index, see [llms.txt](https://docs.customer.io/llms.txt).
> Last updated: July 10, 2026

# Test your emails

After you create your first email, send yourself a test before activating your campaign to make sure your emails render as you’d expect in your inbox.

 Are you using Design Studio to create your email?

You can [send tests from both the email editor and the connected automation](/messaging/design-studio/collaboration/send-test/).

 Are you on a trial?

If you’re on a trial, you’re allowed a [limited number of test emails](/accounts/billing/plan-features/#free-trials) per day.

From any workflow (campaign, broadcast, or transactional message), you can send test messages to make sure your emails look right in your inbox.

1.  Select the email block, and then click **Edit Content**.
2.  Choose a person from the Sample Data panel. Your test send will replace customer liquid statements with this person’s data.
3.  Click **Send test…** above your email.
4.  Enter up to 25 email addresses. Separate multiple email addresses with commas.
5.  Choose whether to include “\[TEST\]” in the subject line.
6.  If your email is translated, you can choose to send tests for all languages; otherwise, test addresses will only get the default message.
7.  Click **Send test**.

**For event-triggered campaigns, you can only test with users who already performed the event.** If they haven’t, you’ll see an error that `event` or `event.<DATA_NAME>` is missing in the “Preview” tab.

 Test emails only send to the addresses you specify

Don’t worry, the email will only send to the address you’ve specified; the customer’s attributes you’re merging in are just for testing purposes. Any email addresses set in the BCC or [Fake BCC](/messaging/channels/email/headers/fake-bcc/) fields will not receive a test message.

If the message includes redacted data (that is, an admin has [hidden sensitive attribute values](/accounts/settings/team/intro-account-access/#hide-sensitive-attributes) from you), then test sends will not show the values for those sensitive attributes.

## If your test email doesn’t arrive

If you send a test email where the *From* and *To* addresses share the same domain (e.g., sending from `notifications@yourcompany.com` to `you@yourcompany.com`), your company’s email server or firewall might flag or block the message. It might think the email is from your domain but originates from an external sending service (Customer.io’s infrastructure), and think it’s spam.

To fix this, you can:

*   **Send tests to a different domain**, like a personal email address.
*   **Allowlist Customer.io’s IPs** in your email server or firewall so it accepts messages from our infrastructure. Contact your IT team or email administrator to set this up. See our [IP allowlist](/accounts/security/ip-addresses/) documentation for more information.

*   *   [If your test email doesn’t arrive](#troubleshooting)

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