How can I apologise for my email gaffe?

Work ethics is a fortnightly feature in Guardian Work where a reader submits a workplace dilemma and asks for your help. A selection of the best answers will appear in Saturday's paper. (And if you have a dilemma you'd like to share, anonymously, with our readers, please email us .) This week's question Recently I emailed a colleague to complain about my boss, rubbishing his management style and personality in general. I was only blowing off steam; however, I accidently copied in the boss. Things have been frosty between us ever since. How can I apologise without appearing insincere? What are your thoughts?