Comment Not Cutting Edge Law (Score 2, Informative) 103
The federal rules for civil procedure (FRCP) were updated in 2006 to address issues like this. Part of the FRCP is what guides production formats during civil suits. A lot of state courts are now using the FRCP as a guide for developing their own standards with regards to management of electronic data for legal purposes. This is the rule, pretty clear. http://www.law.cornell.edu/rules/frcp/Rule34.htm
Previously if you have 10,000 emails you could just print them out to loose piles of paper and turn over boxes (sometimes 100s of boxes) of paper to opposing counsel. After 2006 there is a default that the other side of a lawsuit is entitled to the documents in the same format they are kept in the course of business. This includes meta data and it is specifically mentioned in the FRCP. Most lawyers will make agreements during their discovery conferences (aka 30b6) to agree to production formats that both sides won't find unduly burdensome.