Are internal business e-mails subject to" discovery" under a civil suit?

While you might be able to make the case that some of those emails are outside of the scope of the litigation or that they include trade secrets, as a general matter, your business emails will be subject to discovery in a civil suit. Of course, that is presuming that your business is party to the suit.  If the civil case is a personal matter, your business email will likely be irrelevant.  However, if your business is a party to the lawsuit, your emails are very likely to be part of discovery. For reference: the same is true of your hard-copy business documents.