HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\<ServerName>\Public-<GUID>
registry subkey with the value name Incoming defaults to IPM.Note
and the value data 1 (one), when you send a Simple Mail Transfer Protocol (SMTP) e-mail message to a public folder by using Microsoft Outlook Express or another non-MAPI e-mail client, if the SMTP e-mail message contains one or more embedded e-mail messages, those embedded e-mail messages appear with a message class of IPM.Post instead of IPM.Note.