The Blog

Field notes on deliverability.

Hard-won lessons on email verification, inbox placement, and keeping your sender reputation spotless — from the team building the email verifier you can actually talk to.

Email authentication: SPF, DKIM, DMARC and BIMI

Why Does TXT Record Lookup Fail Despite Correct DNS Setup?

Discover why TXT record lookups for email authentication fail even with correct DNS setup. Learn the real causes and how to fix them with verified tools.

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Free email checker tools: syntax, MX, SMTP, disposable and catch-all checks

How to Verify MX Records Without Falling Into CNAME Loop in Local Testing

Learn how to verify MX records locally without triggering CNAME loops. Avoid testing pitfalls and ensure accurate DNS configuration for email.

Email compliance: CAN-SPAM, GDPR, HIPAA and consent

How to Enforce RFC 4408 Compliance in MAIL FROM During API Integration

Ensure your email API integrations comply with RFC 4408 by validating MAIL FROM domains. Reduce bounces, improve sender reputation, and boost inbox.

Email Verification API & SDKs: the complete developer guide

Email Verification API: SMTP 250 vs 251 for User Engagement Analytics

Use SMTP 250 and 251 responses from an email verification API to improve user engagement analytics. Identify deliverable vs.

Email authentication: SPF, DKIM, DMARC and BIMI

Fixing Email Verification Batch Failure Due to DKIM Domain Key Not Found

Resolve batch verification failures caused by missing DKIM domain keys. Learn how to diagnose and fix DKIM-related issues with real-world steps and tools.

Deliverability, blocklists and sender reputation

How to Identify Spam Sources from SMTP 554 Rejection No Reason

Stop email rejections with no reason. Learn how to trace and eliminate spam sources behind SMTP 554 errors using real-time verification and deliverability.

Email Verification API & SDKs: the complete developer guide

SMTP 569 Closed After Idle Timeout in Email Validation Tool with High Latency

Fix SMTP 569 closed after idle timeout in email validation tools with high latency. Learn how real-time verification reduces errors and improves delivery.

Email authentication: SPF, DKIM, DMARC and BIMI

How to Test SPF DNS TXT Record Validity to Avoid SMTP 554

Prevent SMTP 554 delivery rejections by validating your SPF DNS TXT record. Use real-time tools and best practices to ensure sender reputation and inbox.

Bulk email verification and list cleaning: when and how to verify

Detect and Fix Domain Key Mismatch in Email Sending Infrastructure

Identify and resolve domain key mismatches that block email delivery. Use real-time verification and inbox placement tests to fix SPF, DKIM, and DMARC.

Email authentication: SPF, DKIM, DMARC and BIMI

How to Fix SMTP 554 Error Missing DKIM Domain Key in Batch Verification

Stop batch verification failures due to missing DKIM domain keys. Learn how to diagnose and fix SMTP 554 errors with real tools and accurate email.

Email compliance: CAN-SPAM, GDPR, HIPAA and consent

SMTP 554 Transaction Failed: DKIM Signature Error & How to Fix It

Fix SMTP 554 transaction failures caused by DKIM header signature errors. Learn how to diagnose, prevent, and verify email deliverability with real tools.

Bulk email verification and list cleaning: when and how to verify

SOA Record Integrity Validation for Large-Scale Email Verification Systems

Ensure high deliverability by validating SOA record integrity in large-scale email verification systems.

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Occasional, practical notes on verification and inbox placement. No spam — we'd be embarrassed.