There are two ways to configure accounts for use with active directory.
In the domain/general tab, enter your active directory domain, then set the option to allow auto-create from active directory.
When your user connects and signs in with their email client or webmail, the account will be created and configured.
In the domain/general tab, enter your active directory domain. Create the users mailbox then in their options/password page, set the mailbox password option to active directory.If the mailbox name differs from the active directory name you can specify the active directory name in the ID field of the password options.