And when you say &quot;enterprise&quot;, think also of small and medium businesses.  There are many advantages to webmail, but I keep running into smalls and mediums who use shared hosting for email (IMAP and (shudder) POP3), but can&#x27;t truly leverage &quot;Horde&quot; or other open source webmails.  Their options are Outlook if they have enough licenses ($$), or Thunderbird if they don&#x27;t.<p>Yes, many move to Google&#x27;s infrastructure if they can, but not everyone is able to or wants to.  Thunderbird is one of the remaining alternatives.