To manage the server settings you will need to click on the Settings option in the left hand menu of the webmail interface once logged in.
From there you'll be taken to the Settings page and you can select the Manage Preferences
Once you've clicked on the server settings section you'll get the following options:
Mark the message as read on delete: On/Off
Flag the message for deletion instead of delete: On/Off
Do not show deleted messages: On/Off
Permanently delete messages in the spam folder: On/Off
Clear "Deleted Items" on logout: On/Off
Compact Inbox on logout: On/Off
