You couldn't use it as is, but it wouldn't be too hard to modify. The script has four main sections at the moment:

1. Retrieve articles from server
2. Parse headers, format and spam control
3. Thread and sort
4. Insert into forums

2,3 & 4 can be pretty much left alone (maybe some unneeded stuff can even be taken out). Number one just needs to be changed to get the messages from the mail spool. If you don't fancy doing it yourself I will take a look after I've released a stable(ish) version.