Your emails are going to spam for one of 12 reasons: authentication, reputation, complaints, list hygiene, sending patterns, content, unsubscribe, engagement, identity, domain age, suspicious links, ...
GlockApps, MailReach, Mail Tester and Email on Acid each test inbox placement differently. This guide compares methodology, provider coverage, and use case, separates seedlist testing from content ...
Outlook Focused Inbox splits mail into Focused (priority) and Other (everything else). This guide covers how the classifier works, the signals that push mail one way or the other, Microsoft 365 ...
Gmail sorts inbound mail into 5 tabs: Primary, Promotions, Social, Updates, and Forums. This guide explains how the classifier works, the signals that push mail one way or the other, how to land in ...
Inbox placement rate measures what share of your accepted mail actually lands in the primary inbox, not spam, promotions, or quarantine. This guide covers the difference with delivery rate, the four ...
Hard bounce means permanent failure (5xx, remove the address). Soft bounce means temporary failure (4xx, ESP retries). This guide covers SMTP codes, the most common causes for each, industry ...
Complete guide to Bad Destination Host and “Host Not Found” Email Bounces: Meaning, DNS Causes, and How to Fix Them: syntax, generation, publishing, validation, and common mistakes that break email ...
Complete guide to No MX Records Email Bounces: Meaning, DNS Causes, and How to Fix “No MX for Domain” Errors: syntax, generation, publishing, validation, and common mistakes that break email ...
Complete guide to DNS NXDOMAIN Email Bounces: Meaning, Causes, and How to Fix “Domain Not Found” Errors: syntax, generation, publishing, validation, and common mistakes that break email ...
A practical guide to diagnosing DNS SERVFAIL bounces on outbound email: root causes, resolver behavior, DNSSEC issues, and MX/SPF misconfiguration checklist.
Unsubscribe Blocklist: lists IPs that send mail to addresses that have previously unsubscribed. Targets non-compliance with unsubscribe requests rather than spam content.
Internal blocklist maintained by InterServer hosting. Lists IPs that have sent spam to InterServer-hosted domains. Primarily affects deliverability to addresses hosted on InterServer infrastructure.
