Here's how to implement email address validation on your site using a very simple PHP script.
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README.md

PHP Email Validation

Here's how to implement email address validation on your site using a very simple PHP script.

Important Disclaimer

This script is provided AS IS for educational purposes only.

Script is NOT designed for industrial application and has several known key deficiencies in error tolerance and accuracy / coverage of email address queries.

No warranty or support is provided. Use of this script is at your own risk.

Usage Warning

Many hosting companies do not allow SMTP send operations. Please get permission from your hosting provider before deploying this script.

License

This script is licensed under Apache 2.0.

Installation

Hosting and Platform Requirements

  • PHP capable hosting (e.g. Apache)
  • PHP version > 5.x
  • Hosting provider with port 25 unblocked

Configuration

There is only one thing to configure in this script.

Please set $FROM (line 47) to an email address that makes sense. For example, if you're installing this script on domain "mydomain.com", an appropriate setting for $FROM might be "verify.email@mydomain.com".

How to Install

  • Please configure $FROM setting as above in "Configuration"
  • Upload script "emailverify.php" to hosting provider.

Running the Script

Once uploaded, you can access the script by loading the script in your browser. For example, if you uploaded the PHP script to the root of your domain "mydomamin.com", access is browser @ http://mydomain.com/emailverify.php

Limitations

This is a very simple script and as such suffers from a number of limitations:

  • Limited coverage - does not work very well with some mail services (e.g. Hotmail, Yahoo)
  • Intermittent Connectivity - Your servers IP address can be temporarily or permanently banned with excessive use of this script. When IP blocks happen, the script stops working.
  • Incorrect Results - Results can come back as "Ok" when infact the actual answer is "Bad" (confirmed by sending email to address). This is because script has no way of identifying "catch all" domains. Yahoo is a "catch all" domain and answers "Ok" to all queries.

Where to Find Accurate Email Verification

Industry grade, accurate email verification is a technically advanced and challenging process. Getting it right needs a lot of infrastructure, knowledge and software.

The simple PHP script provided in this Github repository is provided for illustration purposes only and certainly not good enough for serious applications.

For industrial email validation please see my enterprise grade email verification solution provided as a Software as a Service (SaaS) for both bulk list and real time API applications.