Notes on test results when checking mailbox

Note: This article explains why certain test results shown during the verification of the mailbox mail system are inaccurate. The platform performs automated checks for reachability, authentication, and security, but does not always take the specific technical configurations of mailbox into account.

Background

The website internet.nl offers various tests for evaluating domains, websites, and mail systems. The goal of these tests is to verify whether modern Internet standards such as IPv6, DNSSEC, DMARC, or TLS are implemented correctly. During such tests at mailbox, individual results were identified that are not interpreted correctly from a technical perspective. Two of these cases relate to the area of mail security and are explained below.

Authentication of the DMARC report address

The test provided by internet.nl occasionally claims that the address used for DMARC reports is not authenticated. This assessment is not accurate.

mailbox uses a special address with an extension for DMARC reporting:

******@heinlein-support.de

The domain heinlein-support.de, which this address is based on, is fully authenticated and correctly configured. This can be verified using a DNS command, for example:

***********report._dmarc.heinlein-support.de

The output confirming

"v=DMARC1"

shows successful authentication and implementation of the DMARC standard.

The test result displayed by internet.nl therefore does not reflect the actual configuration. The underlying cause is a technical limitation in the test procedure, which currently does not correctly evaluate addresses with extensions (such as +arf).

No connection (on port 25) to an IPv6 address

Another test result concerns the supposedly missing reachability via IPv6 on port 25.

In this context, internet.nl reports a so-called connection timeout. However, this assessment is also inaccurate and is instead the result of an intentional technical measure.

Within the mailbox mail system, certain entries in DNS are deliberately configured so that they are not reachable for external checks or unwanted connection attempts. This improves system security and provides protection against spam attacks.

The test procedure used by internet.nl does not currently take such security measures into account and incorrectly interprets the missing connection as a configuration error.

Summary

The results reported by internet.nl regarding

– authentication of the DMARC report address, and
– reachability via IPv6 on port 25

are technically incorrect and based on incomplete or faulty test logic.

mailbox complies with all relevant Internet and security standards. The affected tests therefore do not provide a reliable assessment of the actual functionality and security of the mail infrastructure.

Note: The operators of internet.nl have been informed about these discrepancies. However, an adjustment of the test logic has not yet been implemented.