<?php
/**
 * Filter the email address to send from and replace the user.
 *
 * @param string $from_email Email address to send from.
 *
 * @return string The new email address.
 */
function wporg_replace_user_mail_from( $from_email ) {
	// This will give us and array with the email user and the domain
	// like this [ 'wordpress', 'example.tld' ]
	$parts = explode( '@', $from_email );

	// Add our new email user, add @ again, and append the domain
	// This will be hello@example.tld
	return 'hello@' . $parts[1];
}

add_filter( 'wp_mail_from', 'wporg_replace_user_mail_from' );