Dovecot:
% cat ssl.crt sub.class1.server.ca.crt > /etc/ssl/dovecot/certs/dovecot.pem
% cp ssl.key /etc/ssl/dovecot/private/dovecot.pem
% cp ca-bundle.crt /etc/ssl/apache2/
dovecot.conf:
ssl_cert_file = /etc/ssl/dovecot/certs/dovecot.pem
ssl_key_file = /etc/ssl/dovecot/private/dovecot.pem
ssl_ca_file = /etc/ssl/apache2/ca-bundle.crt
http://nooms.de/articles/startssl.html
Postfix:
% mv ssl.crt cert.pem
% mv ssl.key key.pem
main.cf:
## TLS parameters ##
smtpd_use_tls=yes
smtpd_tls_cert_file=/etc/ssl/postfix/cert.pem
smtpd_tls_key_file=/etc/ssl/postfix/key.pem
smtp_tls_CAfile = /etc/ssl/apache2/ca.pem
smtpd_tls_loglevel = 3
smtpd_tls_received_header = yes
smtpd_tls_session_cache_timeout = 3600s
tls_random_source = dev:/dev/urandom