[burkaman]

Couldn't you filter most of them out by the timestamp? If you get a reply that was sent faster than a human could have responded, ignore it.

[icebraining]

The auto-reply is probably sent by a desktop email client, which are often offline and/or configured to only check for new email every few minutes. So you'd fail to mark a lot of auto-replies.

[TheSmiddy]

Exchange configures it on the server because generally people have their computers turned off when on holidays.