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
Fix DMARC failures on forwarded mail using ARC. Learn how ARC forwarding works, why DMARC breaks, and how to verify reliable email delivery in 2025.
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Understand how Google Workspace approved senders bypass Gmail filters and why consumer Gmail still blocks emails.
Learn how to implement SPF macros correctly for email service providers. Reduce bounces, improve deliverability, and avoid sender reputation damage with a.
Discover why email verification services trigger false positives in data loss prevention systems—and how MailTester’s 98.9% accuracy prevents unnecessary.
Protect your email deliverability. Discover how domain squatting and no-reply addresses harm inbox placement and how MailTester's verification API stops.
Use confidence intervals to estimate email bounce rate accuracy with statistical rigor. Learn how to apply real-world verification data to improve.
Stop ICS attachments from being blocked. Learn how to verify email lists, test inbox placement, and improve deliverability with real tools — no guesswork.
Understand what negative SpamAssassin scores mean for your email deliverability. Fix scoring issues before they hurt inbox placement.
Migrate your DMARC policy in 2026 with confidence. Reduce email fraud, improve deliverability, and avoid inbox failures.
Understand Exchange Online outbound spam and recipient rate limits. Reduce bounces and improve deliverability with real-time verification and list.
Prevent bounce rates and spam complaints by verifying email addresses before sending. Use real-time checks and inbox placement tests to keep your.
Discover how RFC 9057's Author header improves email reputation management, reduces bounces, and boosts inbox placement.
Stay sharp
Occasional, practical notes on verification and inbox placement. No spam — we'd be embarrassed.
