Contact Form 7 - replace mail content / posted data (in this example replace the email appending the support email domain)

wpcf7_replace_posted_data.php

<?php

function prefix_replace_email( $posted_data ) {

	$posted_data[ 'your-email-backup' ] = $posted_data[ 'your-email' ] ;
	$posted_data[ 'your-email' ] = str_replace('@', 'A', $posted_data[ 'your-email' ]) . '@mysupport.com' ;

	return $posted_data;
}
add_filter( 'wpcf7_posted_data', 'prefix_replace_email' );