WordPress at a glance
filter is not described

pre_user_email filter-hook . WP 2.0.3

Filters a user's email before the user is created or updated.

Usage

add_filter( 'pre_user_email', 'filter_function_name_3397' );
function filter_function_name_3397( $raw_user_email ){
	// filter...

	return $raw_user_email;
}
$raw_user_email(string)
The user's email.

Where the hook is called

wp_insert_user()
pre_user_email
wp-includes/user.php 1557
$user_email = apply_filters( 'pre_user_email', $raw_user_email );

Where the hook is used (in WP core)

wp-includes/default-filters.php 47
add_filter( $filter, 'trim' );
wp-includes/default-filters.php 48
add_filter( $filter, 'sanitize_email' );
wp-includes/default-filters.php 49
add_filter( $filter, 'wp_filter_kses' );