On a VPS with Ubuntu 12.04 server, I have install and configure postfix.
For the SMTP-AUTH I used the mail-stack-delivery package (previously packaged as dovecot-postfix).
sudo apt-get install mail-stack-delivery
After that in /etc/postfix/main.cf I have these two lines:
smtpd_tls_cert_file = /etc/ssl/certs/server.crt smtpd_tls_key_file = /etc/ssl/private/server.key
My question is these files server.crt and server.key are ok OR I have to create others with the openssl (a Self-Signed Certificate).