How to troubleshoot 'Mail delivery failed: returning message to sender' error?I

[ImSimanto]

I'm using a cPanel VPS. Facing an issue with an account on my VPS. When I'm trying to send email I'm getting the error report below:

=========================================================
This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

[email protected]
host gmail-smtp-in.l.google.com [74.125.197.26]
SMTP error from remote mail server after end of data:
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 visit
550-5.7.1 Bulk Senders Guidelines - Gmail Help for more
550 5.7.1 information. 31-v6si12778261plc.173 - gsmtp
Reporting-MTA: dns; thunder.example.com

Action: failed
Final-Recipient: rfc822;[email protected]
Status: 5.0.0
Remote-MTA: dns; gmail-smtp-in.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 visit
550-5.7.1 Bulk Senders Guidelines - Gmail Help for more
550 5.7.1 information. 31-v6si12778261plc.173 - gsmtp
==========================================================

Can anyone please help me in troubleshooting this issue?

 

[rpvw]

This resource has a lot of helpful tips:
How to Keep your Email Out of the Spam Folder - cPanel Knowledge Base - cPanel Documentation

If you are sending mail via a script (eg a contact form) ensure you send via a fully authenticated SMTP protocol (do NOT rely on the php mail() function), using an account that has all the correct MX, PTR, SPF and DKIM (and optionally DMARC) records.

 

[cPanelLauren]

Hello,

Based on the error you're receiving it looks like your domain doesn't have an SPF or DKIM:

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

You can check if your domain has these by running the following:

dig txt yourdomain.com
dig txt default._domainkey.yourdomain.com

If it doesn't have them and your nameservers point to the server the domain is hosted on you can easily add them at cPanel>>Email>>Mail Authentication.


Thanks!