Arkadaşlar Warden Anti-spam and Virus Protection kullananlar için Dovecot 2.4.1 güncelemesinden sonra yaşanan imapve pop3 server probleminin çözümü aşağıda ki gibidir.
/etc/dovecot/conf.d/99-warden.conf dosyasını aşağıda ki gibi düzenleyin;

service imap {
  vsz_limit = 512MB
}

protocol imap {
  mail_plugins = imap_sieve
  sieve_plugins = sieve_imapsieve sieve_extprograms
}service imap {
  vsz_limit = 512MB
}

protocol imap {
  mail_plugins = imap_sieve
  sieve_plugins = sieve_imapsieve sieve_extprograms
}

daha sonra /etc/dovecot/conf.d/90-plesk-sieve.conf dosyasını aşağıda ki gibi düzenleyin;

protocols {
  sieve = yes
}

protocol sieve {
}

protocol lda {
  mail_plugins = sieve
}

sieve_script plesk {
  path = ~/sieve
  active_path = ~/.dovecot.sieve

  sieve_extensions {
    enotify = yes
    imap4flags = yes
  }
}

managesieve_logout_format = "rcvd=%{input}, sent=%{output}"

warden zaman zaman yapacağı sistemsel updatelerde bu dosyaları yine eski versiyonda ki söz dizimine güncelleyeceği için bu iki dosyayı salt okunur hale getirin.

chattr +i /etc/dovecot/conf.d/99-warden.conf
chattr +i /etc/dovecot/conf.d/90-plesk-sieve.conf

dovecot sunucuyu reload edip yeniden başlatın.

dovecot reload
systemctl restart dovecot

English***********
For users of Warden Anti-spam and Virus Protection, the solution to the IMAP and POP3 server issue experienced after the Dovecot 2.4.1 update is as follows.
Edit the /etc/dovecot/conf.d/99-warden.conf file as shown below;

service imap {
  vsz_limit = 512MB
}

protocol imap {
  mail_plugins = imap_sieve
  sieve_plugins = sieve_imapsieve sieve_extprograms
}service imap {
  vsz_limit = 512MB
}

protocol imap {
  mail_plugins = imap_sieve
  sieve_plugins = sieve_imapsieve sieve_extprograms
}

Then edit the /etc/dovecot/conf.d/90-plesk-sieve.conf file as follows;

protocols {
  sieve = yes
}

protocol sieve {
}

protocol lda {
  mail_plugins = sieve
}

sieve_script plesk {
  path = ~/sieve
  active_path = ~/.dovecot.sieve

  sieve_extensions {
    enotify = yes
    imap4flags = yes
  }
}

managesieve_logout_format = "rcvd=%{input}, sent=%{output}"

Since Warden will occasionally update these files to the syntax of the old version during system updates, make these two files read-only.

chattr +i /etc/dovecot/conf.d/99-warden.conf
chattr +i /etc/dovecot/conf.d/90-plesk-sieve.conf

Reload and restart the dovecot server.

dovecot reload
systemctl restart dovecot