Every so often my emails are removed from the following folders: Junk Email, deleted Items or Sent Items

Our mail system will automatically remove emails from the following webmail folders when each email is x number of days old.

Junk Email: 30 days

Deleted Items: 30 days

Sent Items: 60 days

These settings can be changed in the webmail interface under My Settings -> Filtering -> Folder Auto-Clean -> Options: Override auto-clean settings for this account.