The following registry key example shows how to limit the number of messages saved in a given folder by MSDefault.
HKEY_LOCAL_MACHINE\Software\Microsoft\WIS\Control\Device1\Addr1
"MaxMsgs"=3
HKEY_LOCAL_MACHINE\Software\Microsoft\WIS\Control\Device1\Addr2
"MaxMsgs"=6
The folder used for messages that arrive on Addr1 holds three messages. The folder used for messages that arrive on Addr2 holds six messages. As more messages arrive, the oldest messages are deleted.