I'll let a criminal attorney answer that part of it, but he certainly may be able to bring a civil lawsuit against you, depending on what, if any, damages he sustained. If the only damage was an inability to access his email for a short time, I wouldn't think a lawsuit would be justified, although there may be specific facts in his situation that would change this analysis. This doesn't mean what you did was acceptable, quite the contrary.
Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.
I would not consider a lawsuit would be justified. I agree with attorney Swanson.
Good luck to you.
NOTE: This answer is made available by the lawyer for educational purposes only. By using or participating in this site you understand that there is no attorney client privilege between you and the attorney responding. This site should not be used as a substitute for competent legal advice from a licensed professional attorney that practices in the subject practice discipline and with whom you have an atttorney client relationship along with all the privileges that relationship provides. The law changes frequently and varies from jurisdiction to jurisdiction. The information and materials provided are general in nature, and may not apply to a specific factual or legal circumstance described in the question.