I like the idea, but I just don't see startups needing or using an email disclaimer. Plus they are pretty much worthless legal wise - http://www.economist.com/node/18529895 .
Two legally useful email disclaimers: "this is not legal advice" and "this is not an offer to buy or sell securities".
These are both legally binding, because they merely remove potential ambiguity from an email and explicitly state the absence of a contract. Without the disclaimer, the text of an email might otherwise be interpreted to mean that a contract was present.