Free email tools

Four small tools, each with its method published on the same page: what it measures, where every number in it came from, which numbers are approximations, and what it cannot tell you. Three of them run entirely in your browser and send nothing anywhere. The fourth reads public DNS records and keeps no record of what you looked up.

Every one of these pages says how it works before it asks you to type anything. That is not modesty, it is the only way a number on a page is worth anything: a subject line checker that reports "42 characters" without saying which inbox it is talking about, or a size checker that says "too big" without naming the threshold and where the threshold comes from, has given you a verdict you cannot check and cannot argue with. So each tool states its constants, marks the ones that are approximate as approximate — inbox truncation is a pixel measurement being reported in characters, and the character figure moves with the width of the letters you chose — and says outright where it stops. A tool that tells you what it cannot see is more use than one that pretends to see everything.

None of this is a trial of anything, and nothing here asks for an email address. The subject line tester, the size checker and the outline generator are plain functions running in the page you are reading; you can switch your network off and keep using them. The DNS checker has to ask a resolver, so it goes through this site, and the request is rate-limited by address and written to no log and no table: the domain you type is used to build a query and then discarded. If you want to know what 5dayemail.com itself is and what it deliberately does not do, that is set out on the home page, where it can be checked against the software.