Email deliverability, decoded.
Field notes, benchmarks, and practical guides on getting your email into the inbox, from authentication and reputation to content and the filters that decide it all.
Email Deliverability News 2026: What Changed and When Email deliverability news, newest first and updated monthly: Exchange Online's new sending limits, Gmail's verified senders, Apple's relay domain and RFC 9989.
Email Countdown Timers: How They Work and Where They Break An email countdown timer is a GIF drawn when the email opens. The HTML, the free options, where Outlook, Gmail and Apple Mail break it, and which tool to use. What Is Microsoft Smart Network Data Services (SNDS), How to Check It Learn what Microsoft SNDS (Smart Network Data Services) is, how to check it, and how to use it to diagnose and fix email deliverability to Outlook. Email Feedback Loops: Only Two of the Big Four Send You One Yahoo and Microsoft send an ARF report naming the recipient who complained. Gmail sends an aggregate rate with no addresses, and Apple offers none. DANE for Email: Who Publishes a TLSA Record and Who Does Not DANE puts your MX certificate fingerprint in DNSSEC-signed DNS. We checked 13 domains on 22 September 2026: the four large providers publish none. Barracuda Delisting: The Removal Form Says What It Wants Barracuda answers a public DNS lookup honestly and its removal page states its own rules and timing. What the form needs, and what to fix before you file. Blocklist Return Codes: What a 127.0.0.x Answer Actually Means The same 127.0.0.x code means different things on different blocklists. Measured answers from 37 zones, the eight exceptions, and how to read your own result. UCEPROTECT Levels 1, 2 and 3 Are One Operator, Not Three Lists Level 1 is your address, Level 2 your provider's netblock, Level 3 their whole network. Only the first is about you, and only the first has a route you control. Spamhaus Delisting: Which List You Are On Decides the Route Spamhaus is five blocklists and ZEN is three at once. Which one you are on decides whether removal is a click, a form or evidence, and why no browser can check. ARC: a Finished Experiment You Were Never Meant to Deploy ARC is added by forwarders, not senders, and the IETF asked in April 2026 to mark it Historic. What the chain is, who Apple's ask applies to, and what to read. Return-Path: The Address SPF Checks and Your Reader Never Sees What the Return-Path header is, why SPF authenticates it rather than the From address, how a custom return path earns DMARC alignment, and how to read it. DKIM Key Length: 2048 Bits Does Not Fit in One DNS String Why upgrading a DKIM key to 2048 bits breaks the record, how a truncated key still reports its intended size, and the six checks that catch it. SPF include: Over 10 Lookups Does Not Fail Every Message The SPF include mechanism and the ten DNS lookup limit: which terms cost a lookup, why the count is higher than it looks, and who actually fails.
