Well that is one of the limitations of the free Home version, interactive input upon detection. It is one of the few differences between the Home and Pro version of avast, so it isn't crippled in what it detects but isn't a flexible as the pro paid for version.
You don't mention what your email program is as that is crucial to what you 'can' do ?
This assumes you have one that uses the Internet Mail provider.
You only have a limited option in the Home (free) version, to send the infected file to the virus Chest (silent mode, with general answer no, see below).
My own feeling on this is you should use the default interactive action. This way you know exactly what is going on with your system. If you are getting so many warnings, that you want to automate this process, I believe you should review your security practice - filter emails at source, delete from server rather than download them.
See the avast help file, Resident Protection: Standard Shield Provider Settings - "Advanced" Page.
Click on
Internet Mail and then on
Customize.
Go to
Advanced tab and select
Silent Mode and the General answer
No.
