Recently we've seen an increase of authentication policies with Gmail that has impacted users sending to Gmail recipients. This policy requires further proof of authentication of the sending domain. If the sending domain does not prove authentication, users will receive the following warning:
| 550-5.7.1 This message does not have authentication information or fails to pass 550-5.7.1 authentication checks. To best protect our users from spam, the 550-5.7.1 message has been blocked... |
This error is usually caused by misconfigured DNS on the sender's domain.
To correct this, you will need to update the SPF and DKIM on your domain.
SPF for Rackspace Mail: https://www.jucra.com/whmcs/knowledgebase/22/
Enabling DKIM: https://www.jucra.com/whmcs/knowledgebase/21/
We also advise you to check for DMARC: https://www.jucra.com/whmcs/knowledgebase/48/
