While there is a temptation to express your grievances, try not to use this as a place to vent. Resignation letters are not an appropriate place for complaints or critiques of the employer or co-workers.
What you should say: To ease the transition after my departure, I intend to complete all assigned work before my final day and leave thorough instructions for my replacement.
What opportunities did you have here that have impacted your career?
If you're emailing the resignation, you can forgo the address, but keeping it as professional as possible is the name of the game here. October 3, A letter of resignation is written to announce to human resources, superiors, and co-workers your intent to leave your current position.
You can provide feedback on the company in a one-on-one with your boss or coworkers.