Types of formal letters/emails

Types of formal letters/emails:
A letter giving or requesting information
A letter of apology
A letter accepting invitation
A thank-you letter
A letter of complaint
A letter applying for a job
An email congratulating a colleague on a promotion etc.

Who are the formal letters/emails written to?
To people in official position, for example, a manager, a director or another official person who you do not know well or who you haven’t met before.

Who are the formal letters/emails written to?
So, the style of official letters is formal (advanced vocabulary, factual, impersonal language, full verb forms, passive voice, formal linking words/phrases etc), usually using present tenses.
Compare:
…about your taking part - … with regard to your participation in
I really liked… - I was impressed by…
It’ll be great if you can… - I would appreciate it if you could…
Can you send me a bit more info about… - Could you please send me more details about…