This may work to install mail sending/receiving on Manjaro/Arch Linux:

pamac install postfix;touch /var/spool/mail/$(whoami);sudo mkfifo /var/spool/postfix/public/pickup;systemctl enable postfix;systemctl start postfix;sudo newaliases;echo "Message here"|mail -s Subject $(whoami);echo "Done. Read mail by command mail. And then help command to get help."