Chapter 1 - Basic Proxmox VE Installation
1.1 What is Proxmox?
Proxmox VE (Virtual Environment) is an open-source virtualization solution based on Debian. It provides KVM (full virtualization) and LXC (lightweight container) technologies together. It can be installed on a physical server and allows you to host many virtual servers or containers inside.

1.2 System Requirements
64-bit processor (Intel VT-x or AMD-V supported)

Minimum 4 GB RAM (ideal would be 16 GB and above)

SSD/NVMe disk

Static IP recommended

UEFI or Legacy BIOS support

IP KVM, iDRAC, IPMI, or physical access for accessing server

1.3 ISO Download and Preparation
You can download the official Proxmox VE ISO file from the following link:
https://www.proxmox.com/en/downloads

To write ISO to a USB flash drive, Rufus can be used:

Open Rufus

Select ISO

Insert USB

Click Write

1.4 Installation Steps
Start the server from the USB.

Select the option "Install Proxmox VE".

Accept the license agreement.

Disk configuration (ZFS is recommended but for RAID cards, LVM may be more compatible).

Fill in hostname, root password and email.

Enter static IP or enter IP address manually.

Complete the installation, and then when the system reboots, Web GUI will be active.

1.5 Entry to Web Interface
You can afterwards access it from another device using the address below:
https://server_ip_address:8006

Default username: root
Password: Is the one defined during installation.

CHAPTER 2 - Proxmox Configuration and Optimization
2.1 No-Subscription Error Solution
After installing, you will get the error, "No valid subscription". To remove this error, run:

sed -i 's/^deb/#deb/' /etc/apt/sources.list.d/pve-enterprise.list
echo "deb http://download.proxmox.com/debian/pve bookworm pve-no-subscription" > /etc/apt/sources.list.d/pve-no-subscription.list
apt update && apt dist-upgrade -y

2.2 Storage Settings
Local disks appear as local and local-lvm.

External NFS, CIFS, or ZFS storage can then be added.

Adding a storage: Datacenter > Storage > Add

2.3 Network Configuration
Bridge interfaces must be created, e.g., vmbr0.

Static IP definitions can be made via /etc/network/interfaces.

2.4 Backup & Snapshot
Snapshot: Just LVM or ZFS supports it.

Backup: Can be performed to external disks or NAS devices.

For the scheduled backup, from the Web interface: Datacenter > Backup > Add

2.5 Basic Security Settings
SSH port can be changed.

You can install Fail2Ban.

Two-Factor Authentication can be incorporated into the Web interface.

Make the root password complex and unpredictable.

CHAPTER 3 - Setting Up the Mail Gateway on Proxmox
A mail gateway is a system that acts as a filter for all incoming and outgoing emails from an organization to the outside world. It protects against viruses, spam, and blacklisting. Recommended architecture for this arrangement: that the mail gateway is implemented internally inside a Proxmox VM.

3.1 Installing Proxmox Mail Gateway with ISO
Download the Proxmox Mail Gateway ISO from https://www.proxmox.com/en/downloads/category/iso-images-pmg.

Create new VM in Proxmox interface.