Dear (Name), My name is (your name) and I was given your contact details by (your friends name). I hope you that's okay with you. I am writing to you about....,,,,

What is the reason you're contacting him? The tone of your response varies depending on why you're contacting him. For instance if it was regarding a job it would be formal: Dear <name>, My name is <your name>, <your friend's name> passed on your email to me as I'm extremely interested in the <name of job>. Yours sincerely (if you know the name of the person who you are emailing), <your name> If it was more friendly however, i.e. you want to join his amateur hockey club: Hi, <friend's name> gave me your email, I was wondering if I could get some more information about the hockey club, I'm interested in joining ~~~ [be aware that this is not all grammatically correct, as to sound more colloquial and friendly grammar often gets less strict] Cheers! (or thanks a lot) <your name> Hope that helps.

Hello blabla1, My name is blabla2, i am the new (your position) in (company name). I got your email from blabla3, and go on with what you want to ask him or tell him.

How to ask someone I do not know to give me a reference/character reference about the person wanting to rent my house?