There may be some privacy claims, such as intrusion on seclusion or intentional infliction of emotional distress, or privacy violations depending on where and how the individual obtained the contact information or other details in the letter, but it's difficult to evaluate without knowing more about the situation and reviewing the actual correspondence.
The term "cyber bullying" is generally applicable to students. Defamation, false light, slander and libel are applicable to situations where the information is published, not private communications.
There is a tort of Intentional Infliction of Emotional Distress, but it has a very high standard, and must generally constitute behavior that "shocks the conscience" of ordinary people.
There is a criminal statute in Texas that prohibits "repeated electronic communications in a
manner reasonably likely to harass, annoy, alarm, abuse, torment, embarrass, or offend another." (Section 42.07)
There is no exact, magic words that constitute harassment. It just depends on what a reasonable person receiving such communication would believe.
If the communication can be reasonably interpreted as a threat of bodily injury, then that is a felony under Section 22.07.
To make it clear, I would send the person a letter stating that he is not permitted to contact her (or you), especially at work. It's not legally binding on him, but if you send a clear, straightforward letter, it may help demonstrate his intent to annoy or harass, if he continues.
Emotional distress caused by personal injury Premises liability for personal injuries Personal injury Personal injury and defamation Personal injury and libel Personal injury and slander Property liability Felony crime Criminal charges for harassment Criminal charges for stalking Internet law
Sign up to receive a 3-part series of useful information and advice about personal injury law.