Update docs

README.md

@@ -176,6 +176,7 @@ The following tutorials are provided:
 * [Nginx Ingress Controller](docs/tutorials/nginx-ingress.md)
 * [NS1](docs/tutorials/ns1.md)
 * [NS Record Creation with CRD Source](docs/tutorials/ns-record.md)
+* [MX Record Creation with CRD Source](docs/tutorials/mx-record.md)
 * [OpenStack Designate](docs/tutorials/designate.md)
 * [Oracle Cloud Infrastructure (OCI) DNS](docs/tutorials/oracle.md)
 * [PowerDNS](docs/tutorials/pdns.md)

docs/tutorials/mx-record.md

@@ -0,0 +1,28 @@
+# Creating MX record with CRD source
+
+You can create and manage MX records with the help of [CRD source](/docs/contributing/crd-source.md)
+and `DNSEndpoint` CRD. Currently, this feature is only supported by `aws`, `azure`, and `google` providers.
+
+In order to start managing MX records you need to set the `--managed-record-types MX` flag.
+
+```console
+external-dns --source crd --provider {aws|azure|google} --managed-record-types A --managed-record-types CNAME --managed-record-types MX
+```
+
+Targets within the CRD need to be specified according to the RFC 1034 (section 3.6.1). Below is an example of
+`example.com` DNS MX record which specifies two separate targets with distinct priorities.
+
+```yaml
+apiVersion: externaldns.k8s.io/v1alpha1
+kind: DNSEndpoint
+metadata:
+  name: examplemxrecord
+spec:
+  endpoints:
+    - dnsName: example.com
+      recordTTL: 180
+      recordType: MX
+      targets:
+        - 10 mailhost1.example.com
+        - 20 mailhost2.example.com
+```