Zimbra mail has very unique and usable features that make it the world’s best web interface.
The emails can be stored in individual message mode or Conversations with automatic grouping of messages in a message thread. Zimbra email provides Conversations span folders in which Conversations are formed independently of folders meaning messages in different folders can be part of the same conversation. If a message is contributed to a conversation, that conversation is marked as unread and moved to the top of the Inbox. Zimbra mail provides preview pane which enables the user to view a highlighted message preview.
Zimbra provides a functionality of managing Personal folders and their hierarchies which in turn provides the ability to create personal folders and folder hierarchies. Users can generate RSS or ATOM feed based on the contents of the Inbox or other mail folders and enable the user to subscribe to RSS/ATOM feeds.