`emailrelay-check-address-domains.js <emailrelay-check-address-domains.js>`_
----------------------------------------------------------------------------

.. code:: javascript

    //
    // SPDX-FileCopyrightText: 2026 Graeme Walker <graeme_walker@users.sourceforge.net>
    // SPDX-License-Identifier: FSFAP
    // 
    // Copyright (c) 2026 Graeme Walker <graeme_walker@users.sourceforge.net>
    // 
    // Copying and distribution of this file, with or without modification,
    // are permitted in any medium without royalty provided the copyright
    // notice and this notice are preserved.  This file is offered as-is,
    // without any warranty.
    // ===
    //
    // emailrelay-check-address-domains.js
    //
    // An example E-MailRelay filter script for Windows that
    // checks the domain parts of the envelope-from address
    // and all envelope-to recipient addresses against a
    // hard-coded allow-list.
    //
    try
    {
    	// list of allowed domains...
    	var domains = [
    		"books.example.com" ,
    		"xn--bcher-kva.example.de" ,
    	] ;
    
    	function allow_domain( domain )
    	{
    		for( var i = 0 ; i < domains.length ; i++ )
    		{
    			if( domains[i] === domain.toLowerCase() )
    				return true ;
    		}
    		return false ;
    	}
    
    	function match( re , s )
    	{
    		var m = s.match( re ) ;
    		if( !m ) return "" ;
    		return m[1] ;
    	}
    
    	function allow_address( address )
    	{
    		return allow_domain( match( /@(\S*)/ , address ) ) ;
    	}
    
    	// read the envelope
    	var envelope = WScript.Arguments(1) ;
    	var fs = WScript.CreateObject( "Scripting.FileSystemObject" ) ;
    	var ts = fs.OpenTextFile( envelope , 1 , false ) ;
    	var txt = ts.ReadAll() ;
    	ts.Close() ;
    
    	var denied = [] ;
    
    	// check envelope 'from' address
    	var re_from = /^X-MailRelay-From:\s*(\S*)/m ;
    	var address_from = match( re_from , txt ) ;
    	if( !allow_address(address_from) )
    		denied.push( address_from ) ;
    
    	// check envelope 'to' addresses
    	var re_to = /^X-MailRelay-To-[^:]*:\s*(\S*)/gm ;
    	var match_to ;
    	while( (match_to = re_to.exec(txt)) !== null )
    	{
    		var address_to = match_to[1] ;
    		if( !allow_address( address_to ) )
    			denied.push( address_to ) ;
    	}
    
    	// return the result
    	if( denied.length == 0 )
    	{
    		WScript.Quit( 0 ) ;
    	}
    	else
    	{
    		WScript.StdOut.WriteLine( "<<invalid domain>>" ) ;
    		WScript.StdOut.WriteLine( "<<" + denied.toString() + ">>" ) ;
    		WScript.Quit( 1 ) ;
    	}
    }
    catch( e )
    {
    	// report errors using the special <<...>> markers
    	WScript.StdOut.WriteLine( "<<error>>" ) ;
    	WScript.StdOut.WriteLine( "<<" + e.name + ": " + e.message + ">>" ) ;
    	WScript.Quit( 1 ) ;
    }

.. _../examples/emailrelay-check-address-domains.js: emailrelay-check-address-domains_js.html