Because Zarafa uses a so-called Soft Delete system, items removed from view in Outlook can still be restored. This can be done by selecting Tools > Recover Deleted Items.

Select the items which need to be recovered and click on the Restore button to restore the items to the folder they were deleted from. Most items will be restored to the Deleted Items folder.

If Delete is selected, the items will be truly removed from the server, and these items can no longer be recovered. The server has a lifetime on these items, so after a set period of time, the items will be removed.