Synology MailPlus Server Warnings: DNSSEC Validation May Unavailable

Abstract: This article discusses the warning 'DNSSEC validation may unavailable' in Synology MailPlus Server 3.1.6-11332. It provides information about the warning and suggests solutions to resolve the issue.

Created: 2025-03-19 by UserComp.com Editors

Synology MailPlus Server Warnings: DNSSEC Validation May Be Unavailable

When running the Synology MailPlus Server on DSM 7.1.1-42962 Update 8 and MailPlus Server 3.1.6-11332, users may encounter warnings related to DNSSEC validation. This article will provide a detailed overview of DNSSEC, the reasons behind these warnings, and the steps required to mitigate the issue.

What is DNSSEC?

DNSSEC (Domain Name System Security Extensions) is a suite of Internet Engineering Task Force (IETF) specifications for securing certain kinds of information provided by the Domain Name System (DNS) as used on Internet Protocol (IP) networks. It is designed to protect against forged or tampered-with responses and to secure the data integrity.

Understanding the Warning

In this particular scenario, the warning message that appears in the mail log located at /volume1/@maillog/maillog is:

postfix/smtp[13453]: warning: DNSSEC validation may be unavailable: no support in system libraries

This warning implies that the Postfix mail server, which is bundled with Synology MailPlus Server, is not able to perform DNSSEC validation due to a lack of support in the system libraries.

Reasons Behind the Warning

DNSSEC validation may be unavailable due to the following reasons:

Outdated or insufficient system libraries used by Postfix
Incomplete DNSSEC support in the Synology DSM environment

Impact of the Warning

DNSSEC validation is crucial for ensuring data integrity and authenticity in DNS queries. If DNSSEC validation is unavailable, it might increase the risks associated with DNS spoofing attacks and data manipulation.

Mitigating the Issue

To resolve this issue and enable DNSSEC validation, consider the following steps:

Update the DSM version and MailPlus Server to the latest available versions.
Install the libidn2-utils package via the Synology Package Center.
synopkg install libidn2-utils
Reconfigure Postfix to use the updated libraries:

Open the MailPlus Server package.
Select the Services > SMTP tab.
Stop the SMTP service.
Edit the /var/services/homes/MailPlus/Postfix/master.cf file.
Locate the line that starts with smtp inet n -.
Add -o syslog_name=postfix/smtp at the end of the line.
Example: smtp inet n - y - - smtpd -o syslog_name=postfix/smtp

Synology MailPlus Server warnings concerning DNSSEC validation can be resolved by updating the system, installing the required package, and reconfiguring Postfix. By taking these steps, you enhance the security and trustworthiness of your mail system.

References

RFC 4033, 4034, 4035 - DNS Security Introduction and Requirements
Synology DSM 7.1 User Guide: https://www.synology.com/en-global/dsm/7.1/help/general/overview
Postfix DNSSEC Validation: https://www.postfix.org/DNSSEC_README.html

Tags: Linux Synology MailServer DNSSEC

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