What is....Email Hacking (as it Pertains to Harassment and Stalking)?

Email hacking is illicit access to an email account or email correspondence.  Email is a highly used form of communication, and some emails contain personal information, company secrets, and sensitive information. This makes email accounts potentially valuable and is one of the main causes of email hacking.  There are a number of ways in which a hacker can illegally gain access to an email account and majority of them rely on user behavior.

Source: Wikipedia:Email Hacking

In the United States federal justice system, an email hacker may face the following criminal charges:

Computer fraud
Identity theft
Wire fraud
Obstruction of justice

It is important to remember that certain charges that may seem ancillary to the case can actually be crucial; for example, an email hacker that tries to erase his or her tracks may have a hard time trying to disprove the obstruction of justice charge.

Source: Law Dictionary: Criminal Penalties for Email Hacking 

Note: Specifically as it pertains to cyberstalkers, those who perpetrate email hacking (Legally: the unauthorized access to a computer system and illegal impersonation) are often very familiar with those upon whom they focus their attacks.  Spoofing, or using known demographic information about their victims often give these individuals everything they need to access email accounts (through security questions, Social Security numbers, etc.).  If you believe you are, or may become a victim of these malcontents, there are some measures you can take.  Change your email, and all security questions associated to those only you would know.  Even better, Two-Factor Authentication is an excellent way to secure accounts where available.

Applicable Texas Laws: 
Tx Penal Code § 33.07 - ONLINE IMPERSONATION

Applicable Federal Laws: 
18 U.S.C 2701 - STORED WIRE AND ELECTRONIC COMMUNICATIONS AND TRANSACTIONAL RECORDS ACCESS