Sent Mail missing in Horde IMP
From SuperbHosting Support Wiki
The mail server shipped with Plesk for Windows is "MailEnable Standard" which does not include IMAP support. Horde IMP requires IMAP in order to display folders from within it's interface. Both the Professional or Enterprise releases of MailEnable provide IMAP support and will also retain all current mail/accounts and configuration. A license for this software will have to be acquired yourself as SWSoft does not provide this with any Plesk license or add-on.
The following MailEnable knowledge base article provides information on performing this upgrade.
http://www.mailenable.com/kb/Content/Article.asp?ID=me020040
