Create external services section in documentation

Change-Id: I7f845f5e488b02180b8a71f184a71a04b12c40e0
diff --git a/single-master/README.md b/single-master/README.md
index 5b297e5..892a854 100644
--- a/single-master/README.md
+++ b/single-master/README.md
@@ -122,15 +122,6 @@
 You can now run the script to upload them to AWS Secret Manager:
 `add_secrets_aws_secrets_manager.sh /path/to/your/keys/directory`
 
-#### SMTP Service
-
-If you need to setup a SMTP service Amazon Simple Email Service can be used.
-Details how setup Amazon SES can be found [here](https://docs.aws.amazon.com/ses/latest/DeveloperGuide/send-email-set-up.html).
-
-To correctly setup email notifications Gerrit requires ssl protocol on default port 465 to
-be enabled on SMTP Server. It is possible to setup Gerrit to talk to standard SMTP port 25
-but by default all EC2 instances are blocking it. To enable port 25 please follow [this](https://aws.amazon.com/premiumsupport/knowledge-center/ec2-port-25-throttle/) link.
-
 ### Publish custom Gerrit Docker image
 
 * Create the repository in the Docker registry:
@@ -144,9 +135,6 @@
 * Add the plugins you want to install in `./gerrit/plugins`
 * Publish the image: `make gerrit-publish`
 
-NOTE: If you need a testing LDAP server you can find details on how to easily
-create one in the [LDAP folder](../ldap/README.md).
-
 ### Getting Started
 
 * Create a key pair to access the EC2 instances in the cluster:
@@ -177,3 +165,22 @@
 You Gerrit instance will be available at this URL: `http://<HOSTED_ZONE_NAME>.<SUBDOMAIN>`.
 
 The available ports are `8080` for HTTP and `29418` for SSH.
+
+# External services
+
+This is a list of external services that you might need to setup your stack and some suggestions
+on how to easily create them.
+
+## SMTP Server
+
+If you need to setup a SMTP service Amazon Simple Email Service can be used.
+Details how setup Amazon SES can be found [here](https://docs.aws.amazon.com/ses/latest/DeveloperGuide/send-email-set-up.html).
+
+To correctly setup email notifications Gerrit requires ssl protocol on default port 465 to
+be enabled on SMTP Server. It is possible to setup Gerrit to talk to standard SMTP port 25
+but by default all EC2 instances are blocking it. To enable port 25 please follow [this](https://aws.amazon.com/premiumsupport/knowledge-center/ec2-port-25-throttle/) link.
+
+## LDAP Server
+
+If you need a testing LDAP server you can find details on how to easily
+create one in the [LDAP folder](../ldap/README.md).