Email Header & Hop Latency Analyzer
Paste raw RFC 5322 email headers to isolate delivery bottlenecks, calculate the exact transit time between Mail Transfer Agent (MTA) hops, and verify SPF, DKIM, and DMARC authentication.
Parses headers from bottom-to-top to measure MTA transit delays and inspect auth records
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How to Find Raw Email Headers in Major Clients
Raw headers contain the complete routing and cryptographic provenance of an email. Follow these instructions to extract original message headers in standard email providers:
Google Gmail
Web • Workspace- Open the email message in Gmail.
- Click the three vertical dots (More options) next to the Reply icon.
- Select "Show original" from the dropdown menu.
- Click "Copy to clipboard" and paste into our analyzer.
Microsoft Outlook
Desktop • OWA- Web (OWA): Click the three dots (…) > View > View message source.
- Desktop: Double-click to open in a new window.
- Go to File > Properties.
- Copy all content inside the "Internet headers" box.
Apple Mail (macOS)
macOS • iOS- Select the target email in the Apple Mail viewer.
- Navigate to the top menu bar: View > Message > Raw Source.
- Alternatively, press Cmd + Shift + H.
- Select all text and paste into the analyzer.
Understanding MTA Hops: Why Headers are Read Bottom-to-Top
When an electronic mail message travels across the Internet, it does not fly directly from the sender's laptop to your inbox in a single hop. Instead, it moves through a chain of intermediary servers known as Mail Transfer Agents (MTAs)—including submission servers (MSA), outbound smart hosts, anti-spam filters, and inbound Mail Exchangers (MX).
According to standard Internet standards (RFC 5321 and RFC 5322), whenever an MTA accepts an incoming SMTP connection and buffers a message, it prepends a brand-new Received: header to the very top of the existing MIME stream.
Chronological Transit Order vs. Header Stacking
[Top of File] Hop #4: Final Delivery MX (Most Recent Timestamp)
↑ Hop #3: Inbound Spam Filter & Antivirus Scanner
↑ Hop #2: Outbound Relay / Smart Host
[Bottom of File] Hop #1: Originating Client / Web App Submission (Earliest Timestamp)
Because each new server places its stamp on top, reading headers from top to bottom causes confusion because timestamps appear in reverse. Our analyzer reconstructs the chain chronologically from bottom to top, computing the precise mathematical difference (Δt = t_hop − t_previous) to expose exactly where the transmission stalled.
Common Latency Bottlenecks: Identifying the Culprit
When an email experiences unexpected delivery lag, the delay is rarely caused by network bandwidth. Instead, specific defensive filters and queue mechanisms introduce deliberate pauses:
| Bottleneck Mechanism | Typical Latency Delta | Technical Root Cause | Remediation Strategy |
|---|---|---|---|
| Greylisting Defences | 5 to 15 Minutes (300–900s) | The receiving MX returns a temporary 451/421 deferral code to verify if the sender re-attempts delivery like a legitimate RFC-compliant MTA. | Warm sender IP, establish consistent PTR records, or whitelist known transactional IP blocks. |
| DNSBL & IP Reputation Checks | 5 to 30 Seconds | Real-time synchronous lookups against Spamhaus, Barracuda, or multi-RBL DNS matrices timing out under high volume. | Use high-speed caching DNS resolvers (e.g. Unbound/BIND) on receiving mail clusters. |
| Spam Heuristics & OCR Engine | 10 to 60 Seconds | Heuristic scanning (SpamAssassin, Rspamd), attachment decompression, and optical character recognition on embedded PDFs/PNGs. | Scale filter worker concurrency or defer heavy deep-inspection tasks to asynchronous workers. |
| Deferred Spool Queues | 15 Minutes to Hours | The sending domain hit a rate limit (e.g. Google or Yahoo daily volume thresholds) causing outbound queues to defer retry attempts. | Implement automated feedback loop (FBL) monitoring and monitor Postfix/Sendmail active spools. |
Frequently Asked Questions (FAQ)
When a relay hop shows a negative delta (e.g., -4s), it typically indicates timestamp drift between unsynchronized Network Time Protocol (NTP) servers across distinct mail server clusters. If the receiving MTA's local clock is set a few seconds behind the transmitting MTA, mathematical subtraction yields a negative delta even though transmission was instantaneous.
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