SharkDNS guide
5 min readSPF, DKIM, and DMARC checker guide
Verify the DNS policies that protect a domain from spoofing and improve mail delivery.
SPF checkerDKIM lookupDMARC checkeremail authentication
When to use it
Run a mail security check when messages land in spam, after changing mail providers, before a domain migration, or when auditing a domain for spoofing exposure.
What each protocol does
SPF lists authorized sending servers, DKIM signs messages with a domain key published in DNS, and DMARC tells receivers how to handle failures and where to send reports. MTA-STS and TLS-RPT add transport encryption policy and reporting.
Common problems found
The most frequent issues are SPF records exceeding the 10 DNS lookup limit, DMARC stuck at p=none, missing DKIM selectors, and multiple SPF records. Each check reports the exact warning so you can fix the record directly.
More SharkDNS Guides
What is DNS lookup used for?
Use DNS lookup to inspect records, verify routing, troubleshoot mail, and compare public DNS visibility.
Reverse IP lookup explained
Find domains observed on the same IPv4 address and understand shared hosting or infrastructure relationships.
Subdomain discovery for asset inventory
Use public subdomain data to build a cleaner domain inventory and find exposed hosts.