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.
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From there you'll be taken to the Settings page and you can select the Manage Preferences
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Once you've clicked on the server settings section you'll get the following options:
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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