Can I reconfigure access to webmail from http://yourdomain.com/webmail to webmail.yourdomain.com ?

You can do this to allow your users to access webmail.yourdomain.com instead of yourdomain.com/webmail. There are multiple ways to accomplish this. We'll discuss using the cPanel interface.

In the cPanel interface, create a subdomain, webmail.yourdomain.com. Then click on Manage Redirection. Redirect webmail.yourdomain.com to http://yourdomain.com/webmail

Now when going to http://webmail.yourdomain.com you'll be presented with the webmail login screen. You could accomplish something similar with Apache zone file templates if you are the server owner: /usr/local/cpanel/etc/httptemplates.