adduser USERNAME --shell /usr/sbin/nologin
vim /etc/postfix/virtual
postmap /etc/postfix/virtual
vim /etc/postfix/virtual_domains
postmap /etc/postfix/virtual_domains
postfix reload
IMAP over TLS
mail.DOM.TLD 993
TLS on dedicated port
SMTP over TLS
mail.DOM.TLD 587
TLS on dedicated port
