We use a tweaked version of RoundCube WebMail running under a sudomain of the associated domain.

Steps:

• Create the email in the mail area by clicking the Email Accounts icon.
• Create a subdomain in the form mail.yourdomain.com. For the Document Root use something that makes sense, like public_html/mail-yourdomainname
• Install RoundCube with SimpleScripts on this subdomain.
• Tweak RoundCube to make users access the options to change password, Forwarding
  Options, Auto Responders, Configure their local Mail Client (like Outlook), BoxTrapper, Email
  Delivery Route and Email Filtering. Besides we want to mention our own site as the provider of their mail service with a link.
• Tweak RoundCube
  • edit in your RoundCube directory /config/main.inc.php:
    • $rcmail_config['enable_caching'] = TRUE;
    • $rcmail_config['username_domain'] = 'yourwebsite.com';
    • $rcmail_config['create_default_folders'] = TRUE;
    • $rcmail_config['quota_zero_as_unlimited'] = TRUE;
    • $rcmail_config['htmleditor'] = TRUE;
    • $rcmail_config['show_images'] = 1;
    • $rcmail_config['identities_level'] = 0;
  • edit /skins/default/templates/login.html:
    • <p style="text-align:center;"><a href="http://yourwebsite.com/webmail" title="use full email address to log in">change password and other options</a></p>
      <p style="text-align:center;">Your mail provided by <a href="http://yourwebsite.com" title="Professional webdesign">YourWebsite.com</a></p>