Improve documentation with some extra info (hestiacp#3394)

* Add information about SMTP relay

* Fix issue reported by users unable to install via this method

* Add note about default setup

* Update DNS user info exemptions

Author: jaapmarcus

docs/docs/introduction/getting-started.md

@@ -37,14 +37,40 @@ Hestia does not support non-LTS Operating systems. If you install it on, for exa
 
 Interactive installer that will install the default Hestia software configuration.
 
+### Step 1: Download
+
+Download the installation script for the latest release:
+
+```bash
+wget https://raw.githubusercontent.com/hestiacp/hestiacp/release/install/hst-install.sh
+```
+
+If the download fails due to an SSL validation error, please be sure you've installed the ca-certificate package on your system - you can do this with the following command:
+
+```bash
+apt-get update && apt-get install ca-certificates
+```
+
+### Step 2: Run
+
+To begin the installation process, simply run the script and follow the on-screen prompts:
+
 ```bash
-wget -qO - https://raw.githubusercontent.com/hestiacp/hestiacp/release/install/hst-install.sh | bash
+bash hst-install.sh
 ```
 
+You will receive a welcome email at the address specified during installation (if applicable) and on-screen instructions after the installation is completed to log in and access your server.
+
 ## Custom installation
 
 If you want to customise which software gets installed, or want to run an unattended installation, you will need to run a custom installation.
 
+To view a list of available options, run
+
+```bash
+bash hst-install.sh -h
+```
+
 ### List of installation options
 
 ::: tip
@@ -86,7 +112,7 @@ To choose what software gets installed, you can provide flags to the installatio
 #### Example
 
 ```bash
-wget -qO - https://raw.githubusercontent.com/hestiacp/hestiacp/release/install/hst-install.sh | bash -s -- \
+bash hst-install.sh \
 	--interactive no \
 	--hostname host.domain.tld \
 	--email email@domain.tld \

docs/docs/server-administration/dns.md

@@ -22,13 +22,13 @@ With the release of 1.6.0, we have implemented a new API authentication system.
 If you still want to use the legacy API to authenticate with **admin** username and the password make sure **Enable legacy API** access is set to **yes**.
 :::
 
-### DNS Cluster with the Hestia API (Master <-> Master)
+### DNS Cluster with the Hestia API (Master <-> Master) "Default setup!"
 
 ::: warning
 This method does not support DNSSEC!
 :::
 
-1. Create a new user on the Hestia server that will act as a “Slave”.
+1. Create a new user on the Hestia server that will act as a “Slave”. Make sure it uses the username of "dns-user" or has the role `dns-cluster`
 2. Run the following command to enable the DNS server.
 
 ```bash
@@ -47,7 +47,7 @@ There is no limitation on how to chain DNS servers.
 
 ### DNS Cluster with the Hestia API (Master -> Slave)
 
-1. Create a new user on the Hestia server that will act as a “Slave”.
+1. Create a new user on the Hestia server that will act as a “Slave”. Make sure it uses the username of "dns-user" or has the role `dns-cluster`
 2. In `/usr/local/hestia/conf/hestia.conf`, change `DNS_CLUSTER_SYSTEM='hestia'` to `DNS_CLUSTER_SYSTEM='hestia-zone'`.
 3. On the master server, open `/etc/bind/named.options`, do the following changes, then restart bind9 with `systemctl restart bind9`.
 
@@ -147,7 +147,7 @@ v-add-remote-dns-host slave.yourhost.com 8083 api_key '' '' useraccount
 With the new API system, you can also replace `api_key` with `access_key:secret_key`
 
 ::: info
-Please note that currently, only the user `dns-user` is exempted from syncing to other servers. If you have a DNS cluster with multiple master slaves you might run in issues.
+By default the user `dns-user` or user with the role `dns-cluster` are exempted from syncing to other DNS servers!
 :::
 
 ## I am not able to add a server as DNS host

docs/docs/server-administration/email.md

@@ -37,6 +37,12 @@ If not, you have 2 options:
    - [SMTP2GO](https://www.smtp2go.com)
    - [Sendinblue](https://www.sendinblue.com)
 
+## What is an SMTP relay service and how to set it up
+
+SMTP mail relay is the process of transferring an email from one server to another for delivery. Often email from a server is blocked by de service provider due to fear of spam. Or the IP reputation is so low that all email go straight into the spam box. To prevent such issues a lot of companies offer a SMTP relay that takes care of the delivery part. As they send a lot email via the same ip addresses they have a better reputation.
+
+To setup create a account by the provider you want or use and follow their instruction to update your DNS. When completed you can enter the SMTP user account they provider in the settings under "Global SMTP" or under the "Edit mail domain" -> "SMTP relay"
+
 ## I am unable to receive email
 
 If you are unable to receive emails, make sure you have setup your DNS properly. If you are using Cloudflare, disable the use of the proxy for `mail.domain.tld`.