POP3 mail add-on: set unread attribute on fetched mail

- ...to make the new mails show up in the "New E-Mail" query

src/add-ons/mail_daemon/inbound_protocols/pop3/POP3.cpp

@@ -39,6 +39,8 @@
 #include <VolumeRoster.h>
 #include <Query.h>
 
+#include <mail_util.h>
+
 #include "crypt.h"
 #include "MailSettings.h"
 #include "MessageIO.h"
@@ -235,6 +237,7 @@ POP3Protocol::SyncMessages()
 			error = B_ERROR;
 
 		file.WriteAttr("MAIL:size", B_INT32_TYPE, 0, &size, sizeof(int32));
+		write_read_attr(file, B_UNREAD);
 
 		// save manifest in case we get disturbed
 		fManifest.Add(uid);