A. The Exchange Server IS has a flaw. A particular combination of IMAP4 Fetch command parameters makes the Exchange Server IS choke and drop its existing IMAP/SSL connections and stop accepting new connections. Microsoft Product Support Services (PSS) offers a hotfix, but it won't reveal the exact combination of IMAP4 Fetch command parameters because running the command against an unpatched server constitutes a denial-of-service attack. To use the hotfix, you need build 5.5.2560 or later of store.exe, netif.dll, gapi32.dll, and mdbmsg.dll.