The best tool to use to assist the user with viewing the email is RMM, which stands for remote monitoring and management. This is a software that allows the technician to remotely access, monitor, and manage the user's computer and applications. The technician can use RMM to view the user's screen, control the mouse and keyboard, and troubleshoot the email issue. The other tools are not suitable for this task. VNC is a software that allows remote desktop sharing, but it requires the user to install and configure it on their computer, which may not be feasible or convenient. SSH is a protocol that allows secure remote access to a command-line interface, but it is not useful for viewing graphical applications such as email. VPN is a technology that creates a secure and encrypted connection over a public network, but it does not provide remote access or control of the user's computer.