The Blog
Hard-won lessons on email verification, inbox placement, and keeping your sender reputation spotless — from the team that's been verifying email since 2000.
Email authentication: SPF, DKIM, DMARC, BIMI and MTA-STS
Understand DMARC fo tag 0, 1, d, s options and how they impact email deliverability. Use MailTester’s verification to check sender alignment and reduce.
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Ensure OTP emails land in inboxes with dedicated streams or IPs. Use MailTester’s inbox placement tests and verification API to boost OTP deliverability.
Test your email subject lines for spam triggers with a precise spam word checker. Avoid spam filters and boost inbox placement using real-time analysis.
Test inbox placement for movistar.es and telefonica.net addresses. Reduce bounces, improve deliverability with real-time verification and bulk list checks.
Stop the flood of unsolicited mail on Gmail. Identify bad email addresses in your list with MailTester’s 98.9% accurate verification tool and reduce.
Understand exactly how an MTA delivers email step by step — from SMTP handshake to inbox placement.
See how Apple Link Tracking Protection removes UTM parameters and what to do about it. Verify your email list to prevent tracking failures in 2026.
Track the right Google Postmaster metrics in your dashboard to improve inbox placement and sender reputation.
Discover what happens when an email is marked with X-Spam-Flag YES. Learn how spam filters work, why this header is set, and how to prevent it with.
Learn why Outlook dark mode inverts email colors and how to fix it. Prevent visual issues with tested email design practices for better inbox placement.
Implement a DMARC pct=10 quarantine rollout strategy to reduce inbox loss without breaking sender reputation.
Fix responsive email layout issues on iPad. See how landscape mode and Mail app quirks affect inbox placement and design accuracy.
Stay sharp
Occasional, practical notes on verification and inbox placement. No spam — we'd be embarrassed.
