On the Select Mailbox Type page of the Internet E-Mail Migration Wizard, select the type of mailbox that you want to migrate. You can select one of the following types:
By default the migration tools will attempt to use a secure connection to copy mail from the source server using SSL. If your server does not support a secure connection with SSL, then you will need to select the Allow copying Internet mailbox contents over an unsecure connection check box.
Client Access Server
To designate a Client Access Server, select the Specify Client Access Server check box, click Browse, select the Client Access Server, and then click OK.