Sent vs Delivered Comparison
Send a draft to a disposable address from your own account and see what the sending path rewrote — links wrapped in redirects, dropped style blocks, added beacons, the encoding used.
The checker and the preview both reason about a message that has not been sent. This one uses the disposable inbox to find out what a real sending path does to it: open a throwaway address, send the draft from the account it will really go out from, and compare what arrived against what you wrote.
About inbound mail in this deployment
This inbox is real code with an in-memory store, and whether mail from the outside actually reaches it depends on how this instance is deployed: it needs a domain with Cloudflare Email Routing pointed at the ingest Worker (docs/deploying-mail.md). Where that is not wired up, no external message will ever appear here however long you wait — the address is generated, the delivery is not. Nothing on this page pretends otherwise.
Messages are held in memory and vanish on restart. Do not send anything you need to keep.
- 1 Open a throwaway address
- 2 Send your draft to it — from the account it will really go out from
- 3 Pick the message that arrived and compare
How to use it
Open an address
A throwaway address on this service’s domain, valid for a short while and held in memory.
Send from the real account
From the Gmail, Naver or ESP account the campaign will actually go out from. That account’s composer and its link tracking are exactly what is being measured.
Paste the draft and compare
Pick the message that arrived, paste the same HTML you sent, and the comparison lists what was removed, what was added, which links were wrapped in a redirect, and what encoding was used.
Common questions
Will mail I send actually arrive here?
That depends on how this instance is deployed. Inbound mail needs a domain with Cloudflare Email Routing pointing at the ingest Worker; where that is not set up, an address is still generated but no external message will ever appear. The page says so at the top rather than leaving you refreshing.
Why does the comparison happen on the server?
Because a disposable address receives mail from strangers. The inbox never hands the browser raw message markup — only a sanitised copy — and diffing in the browser would mean breaking that rule for every message. So the delivered HTML is read next to the store and only counts, tag names and URL pairs cross, as text.
My draft — is it stored anywhere?
No. It is sent with the comparison request, used, and dropped when the request ends. It is not written to the store, not logged and not returned to anyone.
The message vanished after a while
Inboxes here expire and the store is in memory, so a restart empties it. It is built for one comparison in one sitting, not as a place to keep anything.
Feed it from
HTML Email Compatibility Check
Checks an email’s HTML against what each mail client actually supports, points at the element that breaks, and shows what survives Gmail, Outlook and the rest side by side.
Email Client Support Table
What Gmail, Outlook, Apple Mail, Yahoo, Samsung Mail and Thunderbird support in HTML email, from caniemail’s device tests, with the date each was last tested.
HTML Email Builder
Builds an email from blocks as table-based, inline-styled HTML with a VML-backed button, and writes the plain-text alternative from the same blocks.
Password Generator
Generates random passwords with length, character set and ambiguous-character rules, in bulk if needed.
Next
These accept what this tool produces, so the result can go straight in.
SPF & DMARC Record Builder
Builds valid SPF and DMARC TXT records from a guided form and explains each mechanism it emits.
Email Header Analyser
Parses raw email headers into a delivery timeline with per-hop delays, reads the receiving server’s SPF, DKIM and DMARC verdicts, and flags From/Reply-To/Return-Path mismatches.
HTML Email Compatibility Check
Checks an email’s HTML against what each mail client actually supports, points at the element that breaks, and shows what survives Gmail, Outlook and the rest side by side.
Disposable Email
Gives you a throwaway inbox that receives mail for a limited time, with attachments viewable in place.
CORS Tester
Sends the preflight a browser would send from a chosen origin plus a GET with that Origin, and explains by the Fetch standard’s rules exactly which header blocked it.
Currency Converter
Converts between about thirty currencies at the ECB’s daily reference rates, crossed through the euro, or at a rate you type in.