Some main.cf Postfix settings

header_checks = regexp:/etc/postfix/header_checks

body_checks = regexp:/etc/postfix/body_checks
virtual_alias_maps = hash:/etc/postfix/virtual


message_size_limit = 25600000

smtpd_helo_required     = yes
strict_rfc821_envelopes = yes
disable_vrfy_command = yes

unknown_address_reject_code  = 554

unknown_hostname_reject_code = 554

unknown_client_reject_code   = 554

smtpd_sender_restrictions =
   check_sender_access pcre:/etc/postfix/reject_domains

smtpd_recipient_restrictions =

   check_client_access hash:/etc/postfix/helo_client_exceptions
   permit_sasl_authenticated,
   reject_invalid_hostname,
   reject_non_fqdn_sender,
   reject_non_fqdn_recipient,
   reject_unknown_recipient_domain,
   permit_mynetworks,
   reject_unauth_destination,
   check_recipient_access  hash:/etc/postfix/recipient_access,
   check_client_access hash:/etc/postfix/rbl_client_exceptions,
   reject_rbl_client cbl.abuseat.org,
   reject_rbl_client zen.spamhaus.org,
   reject_rbl_client bl.spamcop.net,
   reject_rbl_client dnsbl.sorbs.net,
   reject_rhsbl_sender dsn.rfc-ignorant.org,
   reject_rhsbl_reverse_client dbl.spamhaus.org,
         permit


# Added for DKIM signing
smtpd_milters           = inet:127.0.0.1:8891
non_smtpd_milters       = $smtpd_milters
milter_default_action   = accept
milter_protocol   = 2

##Should have had already
smtp_tls_security_level = may
smtp_tls_loglevel = 1
# / Added   for DKIM signing