postfix-spamassassin-dovecotがなぜこのように設定されているのですか?

ブラックリストが十分に効果的ではなかったので、最近私のメールサーバーにスパマサシンを追加しました。

明確にするために：私はSMTP用Postfix + LDA用Dovecot、グレーリスト用postgrey、速度制限用postfwdを使用しています。

Spamassassinを追加するには、次のガイドを使用してください。https://www.digitalocean.com/community/tutorials/how-to-configure-a-mail-server-using-postfix-dovecot-mysql-and-spamassassinうまくいきますが、なぜこれが起こるのかわかりません。私をいじめるのはmaster.cfです。

smtp       inet  n       -       y       -       -       smtpd
-o content_filter=spamassassin

dovecot unix    -       n       n       -       -      pipe
  flags=DRhu user=virtual:virtual argv=/usr/lib/dovecot/deliver -f ${sender} -d ${user}@${nexthop} -m ${extension}

spamassassin unix -     n       n       -       -       pipe
user=debian-spamd argv=/usr/bin/spamc -f -e  
/usr/sbin/sendmail -oi -f ${sender} ${recipient}

なぜsendmailが突然関連しているのか理解できません。もっと正確に設定する方法はありますか？

postconf -n必要な場合に備えて、これも私のものです。

append_at_myorigin = yes
biff = no
broken_sasl_auth_clients = yes
default_destination_concurrency_limit = 1
delay_warning_time = 8h
disable_vrfy_command = yes
dovecot_destination_concurrency_limit = 1
dovecot_destination_recipient_limit = 1
enable_original_recipient = yes
local_destination_concurrency_limit = 1
mailbox_size_limit = 100000000
maximal_queue_lifetime = 6d
message_size_limit = 52428800
myhostname = REDACTED
myorigin = /etc/mailname
smtp_helo_name = REDACTED
smtp_use_tls = yes
smtpd_client_restrictions = permit_mynetworks, permit_sasl_authenticated
smtpd_delay_reject = no
smtpd_hard_error_limit = 10
smtpd_helo_required = yes
smtpd_helo_restrictions = permit_mynetworks, reject_invalid_hostname
smtpd_recipient_restrictions = check_policy_service inet:127.0.0.1:10040 permit_mynetworks, permit_sasl_authenticated, reject_non_fqdn_sender, reject_non_fqdn_recipient, reject_unknown_sender_domain, reject_unknown_recipient_domain, reject_unlisted_recipient, reject_unauth_destination, reject_unauth_pipelining, reject_rbl_client zen.spamhaus.org=127.0.0.[2..11], reject_rbl_client bl.spamcop.net, reject_rbl_client cbl.abuseat.org, check_policy_service inet:127.0.0.1:10023
smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unknown_sender_domain, reject_unknown_recipient_domain, reject_unlisted_recipient, reject_unauth_destination, reject_unauth_pipelining
smtpd_sasl_auth_enable = yes
smtpd_sasl_authenticated_header = yes
smtpd_sasl_local_domain = REDACTED
smtpd_sasl_path = private/auth
smtpd_sasl_security_options = noanonymous
smtpd_sasl_tls_security_options = noanonymous
smtpd_sasl_type = dovecot
smtpd_sender_restrictions = permit_mynetworks, reject_unknown_sender_domain
smtpd_soft_error_limit = 5
smtpd_tls_cert_file = REDACTED
smtpd_tls_dh1024_param_file = /etc/ssl/dhparams.pem
smtpd_tls_exclude_ciphers = aNULL, eNULL, EXPORT, DES, RC4, MD5, PSK, aECDH, EDH-DSS-DES-CBC3-SHA, EDH-RSA-DES-CDC3-SHA, KRB5-DE5, CBC3-SHA
smtpd_tls_key_file = REDACTED
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_security_level = may
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
strict_rfc821_envelopes = yes
tls_random_source = dev:/dev/urandom
virtual_alias_maps = proxy:mysql:/etc/postfix/sql/mysql_virtual_alias_maps.cf, proxy:mysql:/etc/postfix/sql/mysql_virtual_alias_domain_maps.cf, proxy:mysql:/etc/postfix/sql/mysql_virtual_alias_domain_catchall_maps.cf
virtual_mailbox_domains = proxy:mysql:/etc/postfix/sql/mysql_virtual_domains_maps.cf
virtual_mailbox_maps = proxy:mysql:/etc/postfix/sql/mysql_virtual_mailbox_maps.cf, proxy:mysql:/etc/postfix/sql/mysql_virtual_alias_domain_mailbox_maps.cf
virtual_transport = dovecot