Run the following commands:
cd /etc/postfix mkdir ssl cd ssl openssl genrsa -rand /etc/passwd:/etc/resolv.conf 2048 > smtpd.key chmod 400 smtpd.key openssl req -new -key smtpd.key > smtpd.csr # Enter the certificate information. # The "common name" is the mail server DNS name.
Run the following commands:
openssl req -days 36524 -x509 -key smtpd.key -in smtpd.csr > smtpd.crt cat smtpd.crt smtpd.key > smtpd.pem
Edit main.cf (located in /etc/postfix/) adding the following at the bottom of the file.
smtp_tls_cert_file=/etc/postfix/ssl/smtpd.pem smtp_tls_key_file=$smtp_tls_cert_file smtp_tls_loglevel=1 smtp_tls_note_starttls_offer=yes smtp_use_tls=yes smtpd_tls_cert_file=/etc/postfix/ssl/smtpd.pem smtpd_tls_key_file=$smtp_tls_cert_file smtpd_use_tls=yes smtpd_tls_received_header=yes
Edit dovecot.conf (typically located in /etc) adding the following lines:
ssl_cert_file = /etc/postfix/ssl/smtpd.pem ssl_key_file = /etc/postfix/ssl/smtpd.pem
Restart postfix and dovecot.