FormalGreeting:
Dear Ms. White, Dear Sir/Madam,
Body:
We are writing to inform you that ...
In regards to your letter from [date] ...
How may we help you?
In order make the necessary repairs we ask you to send the item to ....
Closing:
Thanks for your attention and time.
Yours sincerely,
Yours faithfully,
InformalGreeting:
Hi Ben, Dear Ben,
Body:
How are you?
Many thanks for your (recent/last) letter
I was wondering if you’d like to go to the theatre with me?
Closing:
Anyway, I must go and get on with my work!
Look forward to seeing you again.
Lots of love,