An E-mail client is a computer program or application that allow your download, read, compose and send e-mails. Examples of these programs, amongst many others, include Microsoft Outlook, Windows Live Mail and Mozilla Thunderbird.
Some e-mail clients are commercial offerings (i.e. you have to pay) like Microsoft Outlook, others are free, like Mozilla Thunderbird or Windows Live Mail. Your operating system probably includes a free mail client - in Windows 8 it is the Mail app.
If you don't wish to install or a configure any e-mail client, your Calzada e-mail account is fully accessible through Webmail.
If you wish to use an e-mail client, it has to be configured with your Calzada e-mail account details. This knowledgebase contains step-by-step guides for commonly used e-mail clients:
If you do not use any of the above programs, refer to E-mail server settings.