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.
Cold email deliverability and warm-up
Ensure your cold outreach domains redirect properly to your main website. Avoid deliverability issues with real-time verification and inbox testing.
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Understand if Gmail reputation is tied to domains or streams. Learn how stream separation impacts deliverability and how MailTester’s verification tools.
Stop email rejections from T-Online. Learn why your IP needs an Impressum website and how to verify sender legitimacy before sending.
Learn how MTA retry logic and deferral handling impact email delivery. Reduce bounces and improve inbox placement with real-world insights.
Find out if your cold email domain is burned. Check domain reputation, detect red flags, and verify deliverability risk with real-time email validation.
See the exact syntax and real-world example of the List-Unsubscribe-Post header. Learn how to implement one-click unsubscribe in your emails, improve.
Ensure your emoji subject line renders correctly and avoids spam filters. Use MailTester’s inbox-placement tests to verify deliverability across major.
Use this proven delisting request email template to get removed from spam blacklists fast. Includes real-world wording, step-by-step process, and.
Stop getting 550 5.2.0 Mail rejete OFR_506 errors. Learn the root causes, diagnose bounce patterns, and verify your list with 98.9% accuracy using.
Understand how Apple Mail handles unsubscribe banners and List-Unsubscribe headers. Reduce bounces, improve deliverability, and maintain list hygiene with.
Decode the X-Spam-Checker-Version header and autolearn=ham meaning. Learn how spam filters evaluate your emails and how to improve inbox placement with.
Learn how SpamAssassin’s HTML_IMAGE_ONLY rules evaluate image-to-text ratio and why it impacts deliverability.
Stay sharp
Occasional, practical notes on verification and inbox placement. No spam — we'd be embarrassed.
