This article applies to:

• Trustwave MailMarshal (SEG)

Problem:

• Can't send email to some domains
• SMTP error message similar to: 554 This server requires PTR for unauthenticated connections

Information:

This response indicates that your server does not have a PTR record. Having a valid PTR record is best practice for email servers.

Some email services enforce the policy of requiring a valid Reverse DNS lookup (PTR record) for any email server sending to their servers.

The PTR record does not have to match the HELO name used to send email.

Resolution:

To resolve this issue, configure a DNS PTR record for your SEG server. For help with this requirement, consult your domain registrar, service provider, or persons in charge of DNS service for your network.