Email Reply Analysis Strategies

We'd like replies received in response to Marketo emails to be recorded in a way that would allow us to efficiently analyze the content in the email replies. One method would be to place rules in the email client that is receiving the email replies to forward the replies to a destination email address that would archive all the replies for analysis.

I'm curious what some other approaches might be? Ideally without requiring manual action for each email reply received. We do use Salesforce and will start using Sales Insight but logging inbound email replies in Marketo using Sales Insight appears to be a manual step.