bp_invites_member_invite_get_invitations_by_invited_email( $email )

function bp_invites_member_invite_get_invitations_by_invited_email( $email ) {

	// If the url takes the form register/?bp-invites=accept-member-invitation&email=username+extra%40gmail.com,
	// urldecode returns a space in place of the +. (This is not typical,
	// but we can catch it.)
	$email = str_replace( ' ', '+', $email );

	$args = array(
		'post_type'  => bp_get_invite_post_type(),
		'posts_per_page' => -1,
		'meta_query' => array(
			array(
				'key'     => '_bp_invitee_email',
				'value'   => $email,
				'compare' => '=',
			),
		),
	);

	$bp_get_invitee_email = new WP_Query( $args );

	return $bp_get_invitee_email;
}