What Is a Mail Tester?
A mail tester checks the DNS-based email authentication records configured for a domain — specifically SPF, DKIM, DMARC, and MX records. These records are published as DNS TXT entries and collectively determine whether receiving mail servers will trust, quarantine, or reject email sent from your domain. Email authentication is the foundation of deliverability: without properly configured records, your emails are more likely to be flagged as spam or rejected outright. This is particularly critical for businesses that rely on transactional emails (order confirmations, password resets) and marketing campaigns, where even a small deliverability drop can significantly impact revenue.
How Does It Work?
- Enter any domain name (e.g., gmail.com) in the search field.
- The tool queries DNS TXT records for SPF (v=spf1), DKIM (common selectors like default._domainkey, google._domainkey), and DMARC (_dmarc.domain).
- MX records are checked to verify that the domain has mail exchange servers configured to receive email.
- Each record is evaluated against authentication standards and displayed as a pass, fail, or warning with the raw record value and an explanation of what it means.
Why Email Authentication Matters
Email authentication directly impacts whether your messages reach the inbox or the spam folder. Google and Yahoo implemented stricter authentication requirements in 2024, requiring DKIM and DMARC for all bulk senders (5,000+ messages per day). Without these records, your emails are increasingly likely to be rejected or filtered. Beyond deliverability, email authentication protects your brand from spoofing attacks — where malicious actors send emails that appear to come from your domain. A properly configured DMARC policy with p=reject instructs receiving servers to block any unauthenticated email claiming to be from your domain, preventing phishing attacks that damage customer trust and brand reputation.