main.cf

mydomain_fallback = localhost
message_size_limit = 0
biff = no
mynetworks_style = subnet # was only seen by localhost
mynetworks = 127.0.0.0/8, [::1]/128
#mynetworks = 127.0.0.0/8, 192.168.1.0/24
smtpd_client_restrictions = permit_mynetworks permit_sasl_authenticated permit
recipient_delimiter = +
smtpd_tls_ciphers = medium
inet_protocols = all
inet_interfaces = all
config_directory = /Library/Server/Mail/Config/postfix
virtual_alias_domains = $virtual_alias_maps
virtual_alias_maps = $virtual_maps
recipient_canonical_maps = hash:/Library/Server/Mail/Config/postfix/system_user_maps
smtpd_enforce_tls = no
smtpd_use_pw_server = yes
relayhost = [mail.X]:25
smtp_fallback_relay = [cpanel.Y]:25
smtpd_tls_cert_file = /etc/certificates/Server Fallback SSL Certificate.6D8408A85A861E9E7AE1A6CDE19A336CE8A4DBB0.cert.pem
mydomain = X.pt
smtpd_pw_server_security_options = cram-md5,digest-md5,gssapi
smtpd_sasl_auth_enable = yes
smtpd_helo_required = yes
smtpd_tls_CAfile = /etc/certificates/Server Fallback SSL Certificate.6D8408A85A861E9E7AE1A6CDE19A336CE8A4DBB0.chain.pem
content_filter = smtp-amavis:[127.0.0.1]:10024
smtpd_recipient_restrictions = permit_sasl_authenticated permit_mynetworks reject_unauth_destination
header_checks = pcre:/Library/Server/Mail/Config/postfix/custom_header_checks
myhostname = remote.X.pt
smtpd_helo_restrictions = reject_non_fqdn_helo_hostname reject_invalid_helo_hostname
smtpd_use_tls = yes
smtpd_tls_key_file = /etc/certificates/Server Fallback SSL Certificate.6D8408A85A861E9E7AE1A6CDE19A336CE8A4DBB0.key.pem
enable_server_options = yes
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain, X.pt
mailbox_transport = dovecot
smtp_sasl_password_maps = hash:/Library/Server/Mail/Config/postfix/sasl/passwd
smtp_sasl_auth_enable = yes

######Edit######

smtp_sasl_security_options =
smtp_sender_dependent_authentication = yes
sender_dependent_relayhost_maps = hash:/Library/Server/Mail/Config/postfix/relayhost/maps
relay_domains =
virtual_alias_maps = hash:/Library/Server/Mail/Config/postfix/virtual_domains