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 $ sudo dpkg-reconfigure exim4-config

# Gmail
smtp.gmail.com:account:password

### main/02_exim4-config_options
#################################

disable_ipv6 = true

 $ sudo update-exim4.conf
 $ sudo systemctl restart exim4

...
ENABLED=1
...

chroot = /var/lib/stunnel4/
setuid = stunnel4
setgid = stunnel4
pid = /stunnel4.pid

output = /var/log/stunnel4/stunnel.log

; Authentication stuff
CAfile = /etc/ssl/certs/ca-certificates.crt

; SSL version (古いstunnelだと設定が必要のようだ)
sslVersion = TLSv1

[gmail-smtps465]
client = yes
accept = 127.0.0.1:10465
connect = smtp.gmail.com:465

 $ sudo /etc/init.d/stunnel4 start

127.0.0.1:10465 smtpusername smtppassword

 $ mv .minecraft .minecraft-stable
 $ mkdir .minecraft-forge
 $ ln -s .minecraft-forge .minecraft

 $ minecraft-launcher

 $ sudo iptables -A OUTPUT -d 51.79.83.165 -p tcp -m tcp --dport 443 -j ACCEPT

 $ sudo iptables -A OUTPUT -p tcp -m tcp --dport 443 -j ACCEPT

 $ java -jar forge-1.16.5-36.2.0-installer.jar

 $ cp KimetsunoYaiba_1.16.5_ver30.jar ~/.minecraft-forge/mods/

 $ minecraft-launcher

 $ rm .minecraft
 $ ln -s .minecraft-stable .minecraft