`emailrelay-list-verify.py <emailrelay-list-verify.py>`_
--------------------------------------------------------

.. code:: python

    #!/usr/bin/env python3
    #
    # 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-list-verify.py
    #
    # An example E-MailRelay address verifier script that uses
    # a hard-coded list of recipient addresses.
    #
    
    import sys
    
    try:
    	to = sys.argv[1]
    	domain = sys.argv[4]
    
    	# list of recognised recipient addresses
    	#
    	users = {
    		"alice" : "" , # valid
    		"bob" : "" , # valid
    		"carol" : "carol.smith@"+domain , # valid, with mapping
    		"dave" : "@david" , # local mailbox
    		"erol" : "@" , # local mailbox
    		"malory" : None , # abort
    	}
    
    	# split the recipient address and check the domain part
    	user_part = to.rsplit("@")[0]
    	domain_part = to.rsplit("@")[1]
    	if domain_part.lower() != domain.lower():
    		print("invalid address")
    		print("invalid domain-part ["+domain_part+"]")
    		sys.exit(2)
    
    	# case-insensitive match of the user part
    	user_key = ""
    	user_value = ""
    	for user in users:
    		if user.lower() == user_part.lower():
    			user_key,user_value = user,users[user]
    
    	if user_value is not None and len(user_value) and user_value[0] == "@":
    		# valid local recipient address with a mailbox
    		mailbox = user_value[1:]
    		if len(mailbox) == 0:
    			 mailbox = user_part
    		print(to)
    		print(mailbox)
    		sys.exit(0)
    
    	elif len(user_key) and user_value is not None:
    		# valid recipient address
    		address = user_value
    		if len(address) == 0:
    			address = user_part + "@" + domain
    		print("")
    		print(address)
    		sys.exit(1)
    
    	elif user_value is None:
    		# abort
    		sys.exit(100)
    
    	else:
    		print("invalid address")
    		print("invalid user-part ["+user_part+"]")
    		sys.exit(2)
    
    except Exception as e:
    	t,o,tb = sys.exc_info()
    	print("error")
    	print("exception: ["+str(e)+"] on line "+str(tb.tb_lineno))
    	sys.exit(3)
    

.. _../examples/emailrelay-list-verify.py: emailrelay-list-verify_py.html