Different Types of Personal Letters

How many different types of personal letters do you know?

Here are some different types of letter I have written over the years:
Apologies
Thank you/Appreciation
Complaints
Congratulations
Invitations
Condolences
Advocacy

I would have to say the easiest letters to write are that of thank you/appreciation and the hardest ones are condolences. Over the next couple of weeks I will be giving you more telling you more about each type of letter and giving you an example.

If there are any types of letters you would like to learn about tell me and I will give you an example.