#Postfix Dvecot MySQL setup on Debian based distros (Debian 10,11; Ubuntu 20.04)
#Special thanks to the authors of the following tutorials :
https://github.com/enatsek/ISPMailInstall
https://www.linuxbabe.com/ubuntu/install-roundcube-webmail-ubuntu-20-04-apache-nginx
https://www.linuxbabe.com/mail-server/setup-basic-postfix-mail-sever-ubuntu
https://kb.linuxlove.xyz/mail-server-spf-records.html
https://linuxloser.wordpress.com/postfix/
https://www.adamantmedia.com/mail-server-postfix-dovecot-spamassassin-on-ubuntu-20-04/#setup-mysql-database
https://www.cyberpunk.rs/mail-server-setup-postfix
https://yiworkdisk.netlify.app/en/linux/install_postfix.html
https://codepre.com/set-up-a-mail-server-on-centos-8-using-postfix-dovecot-mysql-and-roundcube.html
https://www.rosehosting.com/blog/how-to-set-up-a-mail-server-with-postfixadmin-on-debian-11/#Step-5-Install-Postfix
https://www.gonscak.sk/?p=643
https://mylinuxtips.info/linuxtipstutorials/setup-mail-server-on-centos7-with-postfix-dovecot-mysql-and-squirrelmail/
https://www.linode.com/docs/guides/email-with-postfix-dovecot-and-mysql/#install-ssl-certificate
https://gist.github.com/Anime4000/59ade3017f1e743069f4e8c6dc032681
https://blog.suenotek.com/post/roundcube-mail-app-and-spf-dkim-dmarc-on-ubuntu-20-04/
https://dmarcian.com/spf-syntax-table/
https://www.sidn.nl/en/news-and-blogs/hands-on-implementing-spf-dkim-and-dmarc-in-postfix
https://docker-mailserver.github.io/docker-mailserver/v10.4/introduction/
https://pestmeester.nl/index.html#10.0
https://jackstromberg.com/2020/01/setting-up-an-email-server-on-a-raspberrypi-postfix-dovecot-mariadb-roundcube/
https://blog.andreev.it/?p=6425#MySQL
https://linuxize.com/post/set-up-an-email-server-with-postfixadmin/
https://github.com/postfixadmin/postfixadmin/blob/master/INSTALL.TXT
https://github.com/mailserver2/mailserver#dns-setup
https://github.com/aqeltech/Dockerised-GUI-Mailserver
Check SPF,DMARC,DKIM,PTR records :
https://www.appmaildev.com/en/spf
https://decoder.link/
https://dnschecker.org/
https://mxtoolbox.com/
https://www.mail-tester.com/