Is the outlook you are using full or Express?
avast has 2 different providers:
1. Internet Mail. It is necessary for Outlook Express (or any other e-mail clients, such as The Bat, Eudora etc.) and in fact, it is this ashmaisv.exe you noted.
2. Outlook plugin. It works only with the full Outlook (not Express), using a special plugin for the program.
To configure any of these providers, you should start the e-mail protection wizard and set the corresponding options (such as inform avast! about the outlook you are using - if it's full or Express, set the accounts you want to protect etc.). Then, when the corresponding provider is running, you can go to the Resident protection settings and fine-tune the rest.
I definitelly wouldn't recommend using regedit to configure your e-mail protection (which probably wouldn't be possible anyway).
Hope this helps.