remove duplicate emails

[Jean-Max Reymond]

Hi,
I have postfix running and sometimes and I have some duplicate emails 
with the same Message-ID.
With dovecot sieve, I understand that duplicate option remove these 
emails but I don't understand the configuration to apply.
Thanks for your tips,

# doveconf -n
# 2.3.7.2 (3c910f64b): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.7.2 ()
# OS: Linux 5.4.0-104-generic x86_64 Ubuntu 20.04.4 LTS
# Hostname: B7B3274.online-server.cloud
auth_mechanisms = plain login
first_valid_uid = 8
log_path = /var/log/dovecot.log
mail_location = maildir:~
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope 
encoded-character vacation subaddress comparator-i;ascii-numeric 
relational regex imap4flags copy include variables body enotify 
environment mailbox date index ihave duplicate mime foreverypart extracttext
namespace inbox {
   inbox = yes
   location =
   mailbox Drafts {
     special_use = \Drafts
   }
   mailbox Junk {
     special_use = \Junk
   }
   mailbox Sent {
     special_use = \Sent
   }
   mailbox "Sent Messages" {
     special_use = \Sent
   }
   mailbox Trash {
     special_use = \Trash
   }
   prefix =
}
passdb {
   args = /etc/dovecot/dovecot-sql.conf.ext
   driver = sql
}
plugin {
   sieve = ~/.dovecot.sieve
   sieve_dir = ~/sieve
}
protocols = imap
service auth {
   unix_listener /var/spool/postfix/private/dovecot-auth {
     group = postfix
     mode = 0660
     user = postfix
   }
}
ssl_cert = </etc/letsencrypt/live/mail.maxou.fr/fullchain.pem
ssl_cipher_list = 
ALL:!LOW:!SSLv2:ALL:!aNULL:!ADH:!eNULL:!EXP:RC4+RSA:+HIGH:+MEDIUM
ssl_client_ca_dir = /etc/ssl/certs
ssl_key = # hidden, use -P to show it
userdb {
   args = /etc/dovecot/dovecot-sql.conf.ext
   driver = sql
}
protocol imap {
   imap_client_workarounds = delay-newmail
   mail_max_userip_connections = 50
}
protocol pop3 {
   mail_max_userip_connections = 10
   pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
}
protocol lda {
   deliver_log_format = msgid=%m: %$
   mail_plugins = sieve
   postmaster_address = postmaster
   quota_full_tempfail = yes
   rejection_reason = Your message to <%t> was automatically rejected:%n%r
}
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