Add IP-based SMTP authentication (#1149)

app/assets/stylesheets/application/elements/_label.scss

@@ -95,6 +95,10 @@
   background-color:$turquoise;
 }
 
+.label--credentialType-smtp_ip {
+  background-color:$orange;
+}
+
 .label--spamStatus-not_checked {
   background:#aaa;
 }