I don't quite understand the question. Whatever method of scanning you use (transparent or using the 127.0.0.1 trick), the avast Mail Scanner service NEEDS to be running. Without it, no mail scanning can be achieved (except for Outlook or TheBat scanning which is handled by specialized plugins).
In short, this service IS the Internet Mail provider. If you stop this provider, the service will be stoped. If you restart the provider, the service will be restarted. Makes sense?
Thanks
Vlk