Relevance: Essential
Putty is an SSH (Secure Shell) client and a server available free of cost. This is useful when you have to access your webserver root for running any scripts.
http://www.putty.org/
Relevance: Essential
FileZilla: This is an excellent FTP client for use on Windows and Linux platforms. If you need to upload and download any files to or from your web server, use this software.
https://filezilla-project.org/download.php
Essential: Filezilla Thunderbird email client
Thunderbird is again an essential software if you want an alternative to Microsoft Outlook. Its free and feature rich.
https://www.mozilla.org/en-US/thunderbird/