Fixes you need after upgrading Debian from 8 to 9


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Run commands:

# Backup files
cp /etc/postfix/ /etc/postfix/
cp /etc/postfix/ /etc/postfix/

# Update and
postconf -e daemon_directory='/usr/lib/postfix/sbin'
postconf -e shlib_directory='/usr/lib/postfix'
postconf -e compatibility_level=2
for i in $(postconf -Mf | grep '^[0-9a-zA-Z]' | awk '{print $1"/"$2"/chroot=n"}'); do postconf -F $i; done


Please remove !SSLv2 from parameter ssl_protocols, and restart Dovecot service:

ssl_protocols = !SSLv3


There's a duplicate parameter in file /etc/fail2ban/jail.conf, under section [pam-generic] like below:

port = all
port = anyport

Comment out port = anyport and restart fail2ban service.