There is an alternative to Zimbra Toaster. It's called Zimbra Notifier and can be downloaded from here
Habitech
It has the following features:
- Notifies due date appointment and e-mails.
- Drag-and-drop file upload support. Upload files into drafts folder. Just drag a file or folder and drop it into ZimbraNotifier app icon.
- Works in all windows versions
- Set zimbra as default mail client, send files to Zimbra directly from MS Office and from windows explorer.
- Does not require installing additional software packages, such as .net framework or java.
- Changes the icon when a new mail arrives and cleans it when it's marked as read or deleted.
- Configurable alert mechanism (modal window, sound, alert balloon in Taskbar Notification Area)
- Obeys polling interval from the Zimbra Preferences
- Very low PC memory requirements
- Define your own notification rules using advanced filters and regular expresions
Bugzilla
Wiki
Source
Zimbra Toaster alternative 
Linear Mode
