What this tool does
This tool evaluates Domain Name System (DNS) records for SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance) to analyze email deliverability. SPF is a protocol that allows domain owners to specify which IP addresses are permitted to send emails on their behalf, reducing spam. DKIM adds a digital signature to emails, enabling the recipient's server to verify that the email content has not been altered. DMARC builds on SPF and DKIM by providing a policy for how email receivers should handle unauthenticated messages from a domain. By checking these records, users can identify misconfigurations and enhance their email reputation, thereby reducing the likelihood of messages being marked as spam.
How it works
The tool retrieves DNS records associated with a domain by querying the DNS database. It checks for the presence and correctness of SPF, DKIM, and DMARC records. For SPF, it verifies that the listed IP addresses match the sender's server IP. For DKIM, it validates the cryptographic signature against the public key published in the DNS. For DMARC, it checks the policy settings defined by the domain owner. The outputs are derived from parsing these records and identifying any discrepancies or misconfigurations.
Who should use this
Email administrators managing corporate email systems need to ensure their configurations meet industry standards. IT security professionals auditing email security protocols for compliance with regulations would benefit from this tool. Marketing teams sending bulk emails must verify SPF, DKIM, and DMARC settings to ensure campaign deliverability. Domain owners configuring their email systems for the first time should confirm that their records are correctly set up to prevent deliverability issues.
Worked examples
Example 1: A company has an SPF record of 'v=spf1 ip4:192.0.2.0/24 -all'. The tool checks if 192.0.2.0 is allowed to send emails for this domain. If an email is sent from 192.0.2.1, it will fail SPF validation because it is not included in the allowed IP range.
Example 2: A domain has a DKIM record with the public key 'v=DKIM1; k=rsa; p=MIGfMA0G...'. The tool verifies the signature in an email against this public key. If the signature generates a match, DKIM validation passes, confirming the email's integrity.
Example 3: For DMARC, a domain owner sets a policy of 'v=DMARC1; p=reject; rua=mailto:[email protected]'. The tool checks if receiving servers comply with this policy. If a non-compliant email is received, it should be rejected based on the DMARC settings, thus enforcing the domain's email policy.
Limitations
The tool may not accurately detect subdomain configurations if they are not explicitly queried. It relies on public DNS records, so any errors in the DNS setup may lead to false results. Additionally, the tool assumes that the DNS propagation is complete, which may not always be the case immediately after changes. It does not evaluate the content of the emails themselves or any anti-spam measures employed by receiving mail servers, which can also affect deliverability.
FAQs
Q: How does SPF record verification handle multiple IP addresses? A: SPF records can include multiple IP addresses or ranges using mechanisms like 'ip4' or 'ip6'. The tool checks all entries to ensure the sending IP is authorized.
Q: What happens if DKIM verification fails? A: If DKIM verification fails, it indicates that the email may have been tampered with, or the signature does not match the public key. This can lead to the email being marked as spam or rejected.
Q: Can DMARC policies be set to 'none'? A: Yes, setting a DMARC policy to 'none' allows monitoring without taking action on unauthenticated emails. However, it is less effective for improving email security compared to 'quarantine' or 'reject'.
Q: How often should DNS records be reviewed for email authentication? A: DNS records should be reviewed regularly, especially after changes to email infrastructure or domain ownership, to ensure continued email deliverability and security.
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