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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? thanks

how someone using my mail relay server to send arbitrary emails via any email address!

Also this is all my configuration on main.cf :

readme_directory = /usr/share/doc/postfix-2.11.5/README_FILES
virtual_mailbox_domains = $virtual_mailbox_maps, hash:/var/spool/postfix/plesk/virtual_domains
virtual_alias_maps = $virtual_maps, hash:/var/spool/postfix/plesk/virtual
virtual_mailbox_maps = , hash:/var/spool/postfix/plesk/vmailbox
transport_maps = , hash:/var/spool/postfix/plesk/transport
smtpd_tls_cert_file = /etc/postfix/postfix_default.pem
smtpd_tls_key_file = $smtpd_tls_cert_file
smtpd_tls_security_level = may
smtpd_use_tls = yes
smtp_tls_security_level = may
smtp_use_tls = no
smtpd_timeout = 3600s
smtpd_proxy_timeout = 3600s
disable_vrfy_command = yes
mynetworks = , hash:/var/spool/postfix/plesk-pop/poplock
smtpd_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/blacklists
smtpd_client_restrictions = permit_mynetworks, permit_sasl_authenticated
smtp_send_xforward_command = yes
smtpd_authorized_xforward_hosts = 127.0.0.0/8 [::1]/128
smtpd_sasl_auth_enable = yes
smtpd_relay_restrictions =permit_mynetworks, permit_sasl_authenticated, defer_unauth_destination, reject_unlisted_sender
smtpd_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_domain
virtual_mailbox_base = /var/qmail/mailnames
virtual_uid_maps = static:30
virtual_gid_maps = static:31
smtpd_milters = , inet:127.0.0.1:12768
non_smtpd_milters =
sender_dependent_default_transport_maps = hash:/var/spool/postfix/plesk/sdd_transport_maps
virtual_transport = plesk_virtual
plesk_virtual_destination_recipient_limit = 1
mailman_destination_recipient_limit = 1
mailbox_size_limit = 0
virtual_mailbox_limit = 0
myhostname = host.com
smtpd_tls_mandatory_protocols = TLSv1 TLSv1.1 TLSv1.2
smtpd_tls_protocols = TLSv1 TLSv1.1 TLSv1.2
smtpd_tls_ciphers = medium
smtpd_tls_mandatory_ciphers = medium
tls_medium_cipherlist = HIGH:!aNULL:!MD5
message_size_limit = 102400000
smtpd_sasl_authenticated_header = yes
disable_vrfy_command = yes
smtpd_sasl_auth_enable = yes
broken_sasl_auth_clients = no
smtpd_sasl_security_options = noanonymous

but the problem is until exists.

0

You can use the smtpd_reject_unlisted_sender PostFix configuration directive, which is documented here.

Note that I'd also make sure to log this and get the person who does this fired immediately (unless it's a typo, of course).

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