dovecot: migrated config to 2.4 + config splitting

data/conf/dovecot/conf.d/10-ssl.conf

@@ -0,0 +1,13 @@
+# /etc/dovecot/conf.d/10-ssl.conf
+# TLS/SSL settings.
+ssl_min_protocol = TLSv1.2
+ssl_cipher_list = ALL:!ADH:!LOW:!SSLv2:!SSLv3:!EXP:!aNULL:!eNULL:!3DES:!MD5:!PSK:!DSS:!RC4:!SEED:!IDEA:+HIGH:+MEDIUM
+ssl_options = no_ticket
+#ssl_dh_parameters_length = 2048
+
+ssl_server {
+  prefer_ciphers = server
+  dh_file = /etc/ssl/mail/dhparams.pem
+  cert_file = /etc/ssl/mail/cert.pem
+  key_file = /etc/ssl/mail/key.pem
+}