User ManualWelcome to's User Guides!Email Discussion Group User Guide TroubleshootingMessage rejected by because Sender does not have Reverse DNS setup.

Message rejected by because Sender does not have Reverse DNS setup.

Reverse DNS is a critical step in authenticating email senders. All legitimate senders of email have this properly configured. Reverse DNS means the name of the host machine sending the email matches the IP address it is sending from.

If not configured correctly, will reject the email.

See this article on Wikipedia for more information -

To verify the mail server is set up correctly, you can use tools like and

Common error messages in this situation.

  • Host lookup failed ( does not match any IP address for


How do I fix this problem?

You will need to work with your upstream ISP to resolve this issue.

Your ISP has assigned you the IP address. They need to update that IP address in this field to point to your mail host name.

When you file a support ticket with the ISP, be sure to provide them with any error messages.

I need to send a message to my list "right now".

While waiting for a technician to fix this problem, you can send a message to the mailing list directly from your account.

Follow the step-by-step instructions in this post: How do I post a message to my list?