For an external service the customer needs in the Active Directory the additional email addresses of the users. According to the documentation this should be done by default in the attribute proxyAdresses of the AD. We have implemented this feature in the AD-Connector, but not in the S4-Connector Ad Mapping looks like that, but I have not found it in S4-Connector mapping. 'mailPrimaryAddress_to_mail': univention.connector.attribute( sync_mode='write', ucs_attribute='mailPrimaryAddress', ldap_attribute='mailPrimaryAddress', con_attribute='mail', ), 'mailAlternativeAddress': univention.connector.attribute( sync_mode='read' if configRegistry.is_true('connector/ad/mapping/user/primarymail') else 'sync', # proxyAddresses.to_mailPrimaryAddress does the write ucs_attribute='mailAlternativeAddress', ldap_attribute='mailAlternativeAddress', con_attribute='proxyAddresses', mapping=( None, proxyAddresses.to_mailAlternativeAddress ), compare_function=proxyAddresses.equal, ),