Do I have to go with the notice of suspension or not???

Well, that's a very unfortunate situation you've gotten yourself into. The HR Head received that message from you, even if it wasn't really meant for her. She has nothing to go by except for the message she received and your reaction to the NTE. It sounds like the message explained itself pretty well. From the HR department's standpoint, your explanation might look like a hasty and ill thought-out attempt to backtrack. With the economy the way it is in my country, sometimes threatening to seek legal advice results in an employee being let go by the company. I sure hope that doesn't happen in your situation. I think the best thing that you could do would write an apology letter to the HR department head. I know it's probably not something that you want to do, but a little bit of humility can go a long way in smoothing things over. If you take responsibility for sending the message to the HR head, even if it was accidental, it will reflect on you a lot better than trying to fight the suspension because the message you sent wasn't intended for her.

You should know first what is your company's policy regarding this. You can talk with your boss and explain your side to him. I think before it should be imposed, the boss will be notify as well. They should hear your side first and with our company, you will be asked make a replay to the written memo then receive it or not. You will not be suspended just like that because everyone deserves a due process, unless they take it personal with you. That is what we have here, I don't know what is yours. I hope you can explain your side as well.

you did the crime, you do the time. it doesn't matter WHO they were intended for, you are guilty of, as you put it, 'using bad words' so you will just have to wait them out. you can seek legal advice but i am sure they will tell you the same thing.

I guest that the NTE will explains your side. Go to your HR department immediately and appeal that it was not meant to other co-employee or you will be guilty if not, nevertheless you should learned also your lesson from this, a workplace is for work and not to make a bad relationship with co-worker. By the way why you need to send a bad words letter to someone like that?