The exchange of e-mail between companies in different states can create personal jurisdiction in a lawsuit when:
the defendant maintains an office in the forum state.
the defendant, at a minimum, has employees that enter the forum state to conduct business.
the e-mail is an integral part of an ongoing business relationship even if no offices or personnel are within the forum state.
the e-mail specifically references a voluntary intention by the parties to submit to the forum state's personal jurisdiction.