I think what Kyle is saying is to create a Rule in Outlook that pulls emails that contain words like "Autoreply" in them into a specific folder. You can do it automatically or just run it when your inbox fills up. I don't believe there is a way to control this from Marketo, its pushed from the recipients email server.
In Outlook:
- Rules > Create Rule... > Advanced Options
- Check off "with [specific words] in the subject or body
- Click on the [specific words] link to fill in "Autoreply", "Out of office", etc
- Move it to the [make a new AutoReplies folder]
- Check off Run this Rule now on messages in [whatever folder they're going to, probably inbox] and check off "Turn on this rule"
- Finish
http://office.microsoft.com/en-us/outlook-help/create-a-rule-HP005242897.aspx