The "550 Bad HELO - Host impersonating domain name" error typically occurs when the sending mail server's HELO or EHLO command does not match the domain name it claims to be sending from. This can happen for several reasons, and here are steps to troubleshoot and fix the issue:
1. Check the HELO/EHLO Configuration
- Ensure that the mail server is configured to use the correct domain name in the HELO/EHLO command. This should match the domain from which the email is being sent.
2. Verify DNS Settings
- Check the DNS records for the domain. Ensure that the A record (or AAAA record for IPv6) points to the correct IP address of the mail server.
- Ensure that the reverse DNS (PTR record) for the IP address matches the domain name used in the HELO/EHLO command.
3. Review Mail Server Configuration
- If you are using a mail server like Postfix, Exim, or Sendmail, review the configuration files to ensure that the hostname is set correctly.
- For Postfix, check the
myhostnameparameter in themain.cffile.
4. Check for IP Spoofing
- Ensure that the sending server is not spoofing another domain. The HELO/EHLO command should reflect the actual sending domain.
5. SPF and DKIM Records
- Ensure that the SPF (Sender Policy Framework) record for your domain includes the IP address of the sending mail server.
- If you are using DKIM (DomainKeys Identified Mail), ensure that it is set up correctly and that the signing domain matches the sending domain.
6. Contact Your Hosting Provider
- If you are unable to resolve the issue, consider contacting your hosting provider or email service provider for assistance. They may have specific configurations or restrictions in place.
7. Test with Different Email Clients
- Sometimes, the issue may be related to the email client being used. Test sending emails from different clients or applications to see if the problem persists.
8. Review Logs
- Check the mail server logs for more detailed error messages that can provide additional context about the issue.
By following these steps, you should be able to identify and resolve the "550 Bad HELO - Host impersonating domain name" error.
