Fix the ‘550 5.7.1 [CS] Message blocked’ MailChannels email error

Definitions

MailChannels is an email delivery service that helps make sure your emails reach your recipients’ inboxes by preventing them from being flagged as spam. It comes included as part of your email service.

The 550 5.7.1 [CS] Message blocked code means that MailChannels flagged your email as spam. However, sometimes your email may not be spam, making the block a false positive.

Below is an example of the 550 5.7.1 [CS] Message blocked email. It always comes with the subject line ‘Mail delivery failed: returning message to sender‘

Before you start

✅ If you get this error and your email is not spam, it’s easy to report and fix.

⚠️ Once you’ve reported the block, wait for an update before sending your email again, this is important to prevent further blocks.

Step by step

1. In the email message, look for the Diagnostic-Code: section and click the provided link

2. On the MailChannels console, click the Not Spam button

ℹ️ Note: If there are blocks to multiple emails, make sure to mark each one as Not Spam.

3. Open a support ticket with our team. In the support ticket, tell us your email has been blocked by MailChannels along with the following information:

• Your email address (the From: address)

• Your recipient’s email address (the To: address)

ℹ️ Note: If there are blocks to multiple emails, make sure to tell us about each one.

4. Wait for an update from our team. Do not try to re-send your email(s) while waiting.

ℹ️ Note: It may take a few hours for the request to process, so please be patient.

5. Once you hear back from our team, resend your email(s)