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 verification and list hygiene for deliverability
Discover how spam traps corrupt blocklists like Spamhaus and hurt sender reputation. Learn how email verification stops this cycle before it starts.
Read article →
Decode X-Forefront-Antispam-Report fields like CIP, CTRY, IPV, and SFV. Understand what they mean and how to use them to improve deliverability and email.
Decide whether using 2 or 3 mailboxes per cold email domain improves deliverability. Use real verification data to avoid bounces, spam traps, and.
Test your Gmail bulk sender compliance with real-time inbox placement and verification. Identify invalid, risky, and banned addresses before sending.
Stop sender reputation damage. Learn how to diagnose and unblock a Microsoft 365 mailbox blocked for spam—step by step with deliverability fixes, sender.
Understand how Apple Mail Privacy Protection and Gmail image caching affect email tracking. Learn what it means for deliverability, engagement, and list.
Learn the real CSA certification requirements and cost for bulk email senders in 2026. Cut bounces, boost deliverability, and avoid blacklists with.
Learn the real impact of secondary domain age on cold outreach success. Use verified data and email validation to avoid blacklists and improve inbox.
Learn what Gmail's 421 4.7.28 error means, why it happens, and how to fix it with real-time email verification to reduce bounces and improve.
Discover how quickly unengaged subscribers hurt email deliverability and learn how to verify and clean your list with real-time tools to improve inbox.
Ensure your T-Online PTR record resolves to a website with Impressum to avoid email delivery issues in Germany. Test and verify with real-time tools.
Learn whether a long email footer increases spam scores. Discover how footer size, content, and structure impact inbox delivery and deliverability — with.
Stay sharp
Occasional, practical notes on verification and inbox placement. No spam — we'd be embarrassed.
