Enable Sieve and ManageSieve for Dovecot

Enables both sieve and managesieved, and adds a global rule that moves
detected spam to a user's Junk folder automatically

site-cookbooks/kosmos_email/templates/dovecot_10-master.conf.erb

@@ -60,6 +60,18 @@ service submission-login {
   }
 }
 
+service managesieve-login {
+  inet_listener sieve {
+    port = 4190
+    ssl = yes
+  }
+  inet_listener sieve_haproxy {
+    port = 14190
+    ssl = yes
+    haproxy = yes
+  }
+}
+
 service lmtp {
   unix_listener /var/spool/postfix/private/dovecot-lmtp {
     mode = 0600

site-cookbooks/kosmos_email/templates/dovecot_20-lmtp.conf.erb

@@ -0,0 +1,9 @@
+##
+## LMTP specific settings
+##
+
+# Enable the Sieve plugin for LMTP delivery so that Sieve scripts are
+# executed for incoming mail handed over by Postfix.
+protocol lmtp {
+  mail_plugins = $mail_plugins sieve
+}

site-cookbooks/kosmos_email/templates/dovecot_90-sieve.conf.erb

@@ -0,0 +1,15 @@
+##
+## Plugin settings (Sieve)
+##
+
+plugin {
+  # Per-user Sieve script storage. The "~" expands to mail_home
+  # (/var/vmail/%d/%n) set in 10-mail.conf, so scripts for LDAP virtual
+  # users are stored under ~/sieve/ with the active script symlinked at
+  # ~/.dovecot.sieve.
+  sieve = file:~/sieve;active=~/.dovecot.sieve
+
+  # Global Sieve script executed AFTER user scripts. Used to enforce
+  # server-side spam filing regardless of per-user rules.
+  sieve_after = /var/lib/dovecot/sieve/after.sieve
+}