Plesk notifications fail delivery: 550-5.7.1 This message does not have authentication information

Symptoms

• This error comes to the admin in a bounce email or is logged to /var/log/maillog

  550-5.7.1 This message does not have authentication information or fails to pass authentication checks. To best protect our users from spam, the message has been blocked.

  550-5.7.26 This message does not have authentication information

• The server doesn't have DKIM or reverse DNS (rDNS or PTR) configured

Cause

Google rejects email if it doesn't have valid rDNS and DKIM records configured.

Resolution

Enable and configure these security features as instructed in our guide for best email practices.