Webmail is an interface linked to your email account that allows a user to connect to their email account from anywhere with an Internet connection and a web browser without configuring it on an email client like Outlook, Thunderbird, etc.
You can access Webmail via a direct link by going to https://webmail.domain.com or https://mail.domain.com/mewebmail, where domain.com is replaced by your domain name.
You will be led directly to the login page of your Webmail. You must enter your full email address and your password to access your mailbox.