ubuntu 12.04 dovecot ssl habilitado, pero ssl_cert no establecido

Su detalle como:

doveconf -n # 2.0.19: /etc/dovecot/dovecot.conf # OS: Linux 2.6.32-042stab120.20 x86_64 Ubuntu 12.04.5 LTS ext4 auth_socket_path = /var/run/dovecot/auth-userdb first_valid_gid = 6 first_valid_uid = 26 hostname = %d lda_mailbox_autocreate = yes lda_mailbox_autosubscribe = yes listen = * mail_gid = mail mail_location = maildir:/var/mail/%d/%n mail_plugin_dir = /usr/local/lib/dovecot mail_uid = mailnull passdb { args = /usr/local/etc/dovecot/dovecot.sql driver = sql } postmaster_address = postmaster@%d protocols = imap sendmail_path = /usr/local/sbin/exim service auth { unix_listener auth-userdb { group = $mail_gid mode = 0600 user = $mail_uid } } service imap-login { inet_listener imap { port = 143 } } service pop3-login { inet_listener pop3 { port = 110 } } userdb { args = /usr/local/etc/dovecot/dovecot.sql driver = sql } doveconf: Error: ssl enabled, but ssl_cert not set protocol pop3 { pop3_client_workarounds = outlook-no-nuls oe-ns-eoh } protocol imap { imap_client_workarounds = delay-newmail tb-extra-mailbox-sep tb-lsub-flags mail_plugins = quota imap_quota antispam } doveconf: Fatal: Error in configuration file /etc/dovecot/dovecot.conf: ssl enabled, but ssl_cert not set