Email Header Analyzer

When an email goes missing, lands in spam, or takes 10 minutes to arrive, the headers hold every answer you need. Email headers are metadata that every mail server adds as your message hops from sender to recipient. They record authentication results, server timestamps, IP addresses, and routing decisions. Paste your headers into this analyzer and you'll see exactly what happened — and where things went wrong.

What's actually in email headers

Every email carries a stack of headers that gets built bottom-up as the message travels. The oldest headers are at the bottom, the newest at the top. Key headers include: Received (one per server hop, with timestamps), Authentication-Results (SPF, DKIM, DMARC verdicts), From and Return-Path (which may differ — that's important), Message-ID (unique identifier), and X-Spam-Status (spam filter scores). Our analyzer parses all of these and presents them in a readable timeline.

Debugging authentication failures

The most common reason emails hit spam is authentication failure. The Authentication-Results header tells you exactly which checks passed or failed. If SPF failed, the sending IP isn't in your SPF record. If DKIM failed, the signature couldn't be verified — maybe the DNS record is wrong or the message was modified in transit. If DMARC failed, neither SPF nor DKIM aligned with your From domain. This analyzer highlights failures in red so you can spot them instantly.

Finding delivery delays

Each Received header includes a timestamp. By comparing consecutive timestamps, you can pinpoint exactly where your email sat waiting. A 200ms gap between hops is normal. A 45-second gap means that server was doing something slow — probably spam filtering or greylisting. If you see delays of 5+ minutes, the receiving server might be applying rate limits to your IP, which often happens during email warmup.

Common header analysis mistakes

Don't confuse the From header with the Return-Path (envelope sender). They're often different, and SPF checks the Return-Path domain, not the From domain. Another mistake: assuming a "pass" on all three auth checks means your email will reach the inbox. Authentication is necessary but not sufficient — content filtering, sender reputation, and engagement history all play roles too. Check your domain against blacklists and run a deliverability score check for the full picture.