The ability of any apology letter to be classified as a good apology letter lies in the content and context onto which it begs to carry. Initially it is understood that the apology letter offers to bridge the gap created by the inability of the sender to issue a product or a service or explain a wrongdoing. A good apology letter is one that carries the message across without twisting the facts or negating the circumstances of which the writer is acknowledging as his fault.
It is a way of admitting liability and seeking forgiveness or amnesty from the recipient without ending the previous relationship by sounding unabashed. The sender is also supposed to steer clear of any humor or metaphors that may tend to float the wrong impression of remorse, and should stick to simple words that create a feeling of sympathy and request for a chance at reconciliation. Only then can the apology letter pass for a good letter.