This is strange, avast! detect a virus, you chose delete it and it was not deleted… Are you sure that the ‘infected’ attachment file, beside the others (if any) was not deleted?
I do the same. You must be using the Pro version (or you wouldn’t be able to automatically delete the infected messages). Is this that you mean with ‘instantly’ or you have to click the buttom ‘delete’?
We all are impressed, day after day ;D