DOCS: Migrated documentation website to Gitbook (#1809)

documentation/functions/domain/MX.md

@@ -0,0 +1,26 @@
+---
+name: MX
+parameters:
+  - name
+  - priority
+  - target
+  - modifiers...
+parameter_types:
+  name: string
+  priority: number
+  target: string
+  "modifiers...": RecordModifier[]
+---
+
+MX adds an MX record to the domain.
+
+Priority should be a number.
+
+Target should be a string representing the MX target. If it is a single label we will assume it is a relative name on the current domain. If it contains *any* dots, it should be a fully qualified domain name, ending with a `.`.
+
+```javascript
+D("example.com", REGISTRAR, DnsProvider(R53),
+  MX("@", 5, "mail"), // mx example.com -> mail.example.com
+  MX("sub", 10, "mail.foo.com.")
+);
+```