How to make Rules ignore case sensitivity when comparing strings
Make a custom module called 'email_lowercase' and place this code inside it, before runnin this new action, do on both emails 'convert a data type' to 'text', then run the new action this custom module provides with Example@example.com TEXT-token-value you have just converted. After running custom action it will return a TEXT in lowercase, then comapre your email1-text-converted with the TEXT returned from custom module.

Note: you will nedd rules conditional module to compare (add conditional, add an IF) your variables AFTER this custom action is triggered.
Done.

&lt;?php
/**
* Implement hook_rules_action_info()
* Declare any meta data about actions for Rules
*/

function email_lowercase_rules_action_info() {
 $actions = array(
  'email_lowercase_action' =&gt; array(
    'label' =&gt; t('Convert to lowercase a TEXT email'),
    'group' =&gt; t('custom'),

    'parameter' =&gt; array(

        'email' =&gt; array(
                'type' =&gt; 'text',
                'label' =&gt; t('$text-variable-token-Email to be lowercase'),
                ),
    ),


    'provides' =&gt; array(
      'email_lower_case' =&gt; array(
        'type' =&gt; 'text',
        'label' =&gt; t('email in lower case'),
      ),
    ),
  ),
);
  return $actions;
}

// rules function numero a texto
function email_lowercase_action($email) {
  $email_lower_case = array();
  $email_lower_case = strtolower($email);

  return array (
  'email_lower_case' =&gt; $email_lower_case,
 );
}


NOTE: there are no EMAIL data types for rules, thats way i suggested to firts convert an email field to text. It may work if you don't, i did not tryed that.