What does this do?

This web service tests any email address to see if it complies with the standards set out in the internet RFCs.

It doesn't check if a particular address actually exists - you can only do that by trying to send an email to it.

If you want to know more about email address validation, read the About page

How to use the email address validation service

The email address validation service has a REST API. The validation results can be returned as semantic HTML, JSON, JSONP or XML.

In general you would validate an email address like this: https://isemail.info/<method>/<address> where <method> is one of the methods described below and <address> is the address you want to validate.

Default method

If you just use https://isemail.info/<address> then the validator will return information about <address> in the default HTML format.

There are some reserved words you can't test like this, for instance https://isemail.info/help and https://isemail.info/about and all the methods documented below.

Putting an email address into a URL

Note the address must be URL-encoded if it contains characters that have a special meaning in a URL. In other words, if you try to validate a#[email protected] then the # and everything after it will not be forwarded to the server (try it).

The way to avoid this is to use appropriate URL entities where necessary. The address above can be validated by putting a%[email protected] into the URL.

If you type an address into the text box then the URL-encoding will be done for you.


Here are the methods you can use

e.g. https://isemail.info/json/[email protected]
Returns comprehensive information about [email protected] as JSON data.
e.g. https://isemail.info/jsonp=myFunction/[email protected]
Returns a valid line of Javascript calling the function myFunction with comprehensive information about [email protected].
e.g. https://isemail.info/xml/[email protected]
Returns comprehensive information about [email protected] as XML data.
e.g. https://isemail.info/html/[email protected]
Returns comprehensive information about [email protected] in HTML format (this is the default).
e.g. https://isemail.info/basic/[email protected]
Returns brief, basic information about [email protected] as an HTML fragment.
e.g. https://isemail.info/valid/[email protected]
Returns 1 for a valid RFC 5321 Mailbox, 0 otherwise.
e.g. https://isemail.info/diagnosis/[email protected]
Returns the specific diagnostic text for this address.
e.g. https://isemail.info/category/[email protected]
Returns the general diagnostic category for this address.
e.g. https://isemail.info/numeric/[email protected]
Returns the specific diagnosis for this address as an integer.
e.g. https://isemail.info/constant/[email protected]
Returns the specific diagnosis for this address as a constant name.
e.g. https://isemail.info/categoryconstant/[email protected]
Returns the general diagnostic category for this address as a constant name.
e.g. https://isemail.info/smtp/[email protected]
Returns the likely SMTP extended return code for this address as text.
e.g. https://isemail.info/reference/[email protected]
Returns any relevant passages from the RFCs that help to support the diagnosis for this address.

Behaviour note

What if you are testing an address that is the same as a method name? Here's what happens:

https://isemail.info/<method> tests <method> as if it was an address.

https://isemail.info/<method>/ (note the trailing slash) tests the empty string and returns the results in the format specified by <method>.