An email about bounce is sent by server to the administrator:
Reporting-MTA: dns; example.com
X-Postfix-Sender: rfc822; [email protected]
Arrival-Date: Fri, 13 Oct 2017 03:45:16 -0500 (CDT)
Final-Recipient: rfc822; [email protected]
Remote-MTA: dns; ASPMX.L.GOOGLE.COM
Diagnostic-Code: smtp; 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. Please
https://support.google.com/mail/answer/81126#authentication for more 550
5.7.1 information. e99si513617itd.159 - gsmtp
If the notification sent via Cron the next error can be found in the
550-5.7.26 This message does not have authentication information or fails to 550-5.7.26 pass authentication checks. To best protect our users from spam, the 550-5.7.26 message has been blocked. Please visit 550-5.7.26 https://support.google.com/mail/answer/81126#authentication for more 550 5.7.26 information.
Server does not have SPF and DKIM set-up
Server does not have a valid rDNS
Server’s IP is blacklisted
Google requirements for mail servers is to have at least a valid rDNS and enabled SPF and DKIM to be able to deliver email messages.
Remove server’s IP address from blacklists:
- Navigate to spam list’s server
- Follow the delisting procedure
Enable SPF and DKIM:
Navigate to Tools & Settings > Mail Server Settings
Set DKIM spam protection and Enable SPF spam protection to check incoming mail to active
Note: Domain DNS must be delegated to Plesk for DKIM and SPF records to be applied automatically. In other words, NS record for the domain should point to Plesk IP address in domain registrar panel.