http://drupal.org/project/cpanel_api
Includes admin interface for setting cPanel user and pass, SSL and port.Currently provides functions for:
Mail - add, delete, edit pass, edit quota
FTP - add, delete, edit pass, edit quota
MailMan - add list, delete list, edit pass
http://drupal.org/project/webmail_plus
Webmail Plus is a full-featured email client for Drupal. It's designed to provide email for any or all members of a Drupal site
http://drupal.org/project/imap_auth
http://drupal.org/project/mailserver
http://drupal.org/project/mail_api
http://drupal.org/project/aes
http://drupal.org/project/bitcache
http://drupal.org/project/rdf