There are times when dashing off an angry letter or email may be very gratifying.
It is understandable that one would want to put down on paper the feelings of frustration, embarrassment or betrayal.
All of that is human.
Just never send it.
Let your anger cool. Reconsider your initial analysis of the other person's motives. Look at the bigger picture. Ask yourself if an angry note will truly advance your cause.
In many cases, it won't. Indeed, it may even be used as evidence that you are rash or high-strung or not a team player. You may wind up as the main victim of your outburst.
Far better that you wait a while and then arrange a meeting with or call the other person. Those hotly worded letters and email messages have a habit of being saved and forwarded.
I've yet to see one that furthered a career.