The Blog

Field notes on deliverability.

Hard-won lessons on email verification, inbox placement, and keeping your sender reputation spotless — from the team that's been verifying email since 2000.

Inbox placement by mailbox provider: Gmail, Outlook, Yahoo and spam filters

Gmail Spam Signals Caused by Poor Email List Hygiene

Discover how bad email list hygiene triggers Gmail spam filters. Learn to verify emails, reduce bounces, and improve inbox placement with real tools and.

Read article →

Deliverability testing inside your ESP, CRM and sending platform

Migrating from Mailgun to Postmark Checklist 2026

Ensure a smooth transition from Mailgun to Postmark with this actionable checklist. Verify your list, test deliverability, and avoid downtime.

Email verification and list hygiene for deliverability

How to Remove Recycled Spam Traps from an Old Email List

Clean your old email list by removing recycled spam traps. Use real-time verification to identify invalid, risky, and trap addresses before sending.

Deliverability testing inside your ESP, CRM and sending platform

IP Pool Strategy on Amazon SES Configuration Sets

Optimize your Amazon SES deliverability with a proven IP pool strategy. Reduce bounces, boost inbox placement, and protect sender reputation using.

Sender reputation, IP warm-up and sending infrastructure

Apple's Email Filtering Algorithms and Their Impact on Sender Reputation

Discover how Apple's email filtering algorithms affect sender reputation and inbox placement. Use MailTester’s real-time verification to fix.

Bounce codes and SMTP errors explained

Yahoo Mail Bounce Rate Impact on Bulk Email Deliverability

Reduce Yahoo Mail bounce rates and improve bulk email deliverability with real-time verification and inbox placement testing. Start with 100 free checks.

Inbox placement by mailbox provider: Gmail, Outlook, Yahoo and spam filters

How to Read the Return-Path in Gmail Show Original Headers

Learn how to read the return-path in Gmail’s Show Original headers to debug delivery issues and improve email deliverability.

Anti-spam laws and compliance: CAN-SPAM, GDPR, CASL

Postmaster Tools v2 Says Compliant But Emails Still Go to Spam

Fix why Postmaster Tools v2 says compliant but emails still land in spam. Learn actionable steps to improve inbox placement and reduce spam folder.

Sender reputation, IP warm-up and sending infrastructure

JMRP Complaint Email Arrives Redacted? How to Identify the User

Learn how to identify the complainer behind a JMRP complaint email with redacted recipient. Use real-time verification and inbox testing to prevent.

Sender reputation, IP warm-up and sending infrastructure

Which Mailbox Providers Send ARF Complaint Reports in 2026?

Find exactly which mailbox providers send ARF complaint reports. Learn how to use ARF data to improve deliverability and reduce spam complaints in 2026.

Deliverability monitoring, metrics and reporting

Subdomain Naming Conventions for Email: News, Tx, Alerts Examples

Learn best practices for email subdomain naming conventions with real examples for news, tx, alerts.

Deliverability testing tools compared: alternatives and reviews

Postmark vs Mailgun Account Approval and Domain Review 2026

Compare Postmark vs Mailgun account approval and domain review. Learn how each handles verification, setup speed, and domain validation to avoid inbox.

Stay sharp

Get deliverability tips in your inbox.

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