assume that, you have a pop3 email address saved on your outlook or other mail clients, if you changed your user information in account setting like the following attachment you can send any@any.com email.my mail service is postfix and i set all the sender and recipient restriction such as reject_unlisted account or reject non fqdn domains or hostname but it's not worked! how you fix this problem in your enterprise mail services?thanksAlso this is all my configuration on main.cf :readme_directory = /usr/share/doc/postfix-2.11.5/README_FILESvirtual_mailbox_domains = $virtual_mailbox_maps, hash:/var/spool/postfix/plesk/virtual_domainsvirtual_alias_maps = $virtual_maps, hash:/var/spool/postfix/plesk/virtualvirtual_mailbox_maps = , hash:/var/spool/postfix/plesk/vmailboxtransport_maps = , hash:/var/spool/postfix/plesk/transportsmtpd_tls_cert_file = /etc/postfix/postfix_default.pemsmtpd_tls_key_file = $smtpd_tls_cert_filesmtpd_tls_security_level = maysmtpd_use_tls = yessmtp_tls_security_level = maysmtp_use_tls = nosmtpd_timeout = 3600ssmtpd_proxy_timeout = 3600sdisable_vrfy_command = yesmynetworks = , hash:/var/spool/postfix/plesk-pop/poplocksmtpd_sender_restrictions = reject_unknown_sender_domain,reject_unauthenticated_sender_login_mismatch,reject_known_sender_login_mismatch,hash:/var/spool/postfix/plesk/blacklists, permit_sasl_authenticated, check_client_access, pcre:/var/spool/postfix/plesk/non_auth.re, check_sender_access hash:/var/spool/postfix/plesk/blacklistssmtpd_client_restrictions = permit_mynetworks, permit_sasl_authenticatedsmtp_send_xforward_command = yessmtpd_authorized_xforward_hosts = 127.0.0.0/8 [::1]/128smtpd_sasl_auth_enable = yessmtpd_relay_restrictions =permit_mynetworks, permit_sasl_authenticated, defer_unauth_destination, reject_unlisted_sendersmtpd_recipient_restrictions = reject_unknown_sender_domain,reject_non_fqdn_sender,permit_mynetworks,permit_sasl_authenticated, reject_unauth_destination, reject_unauth_destination, defer_unauth_destination,reject_unverified_recipient,reject_unknown_recipient_domainvirtual_mailbox_base = /var/qmail/mailnamesvirtual_uid_maps = static:30virtual_gid_maps = static:31smtpd_milters = , inet:127.0.0.1:12768non_smtpd_milters =sender_dependent_default_transport_maps = hash:/var/spool/postfix/plesk/sdd_transport_mapsvirtual_transport = plesk_virtualplesk_virtual_destination_recipient_limit = 1mailman_destination_recipient_limit = 1mailbox_size_limit = 0virtual_mailbox_limit = 0myhostname = host.comsmtpd_tls_mandatory_protocols = TLSv1 TLSv1.1 TLSv1.2smtpd_tls_protocols = TLSv1 TLSv1.1 TLSv1.2smtpd_tls_ciphers = mediumsmtpd_tls_mandatory_ciphers = mediumtls_medium_cipherlist = HIGH:!aNULL:!MD5message_size_limit = 102400000smtpd_sasl_authenticated_header = yesdisable_vrfy_command = yessmtpd_sasl_auth_enable = yesbroken_sasl_auth_clients = nosmtpd_sasl_security_options = noanonymousbut the problem is until exists.
send fake email using mail clients
postfix