Cheerio

Why is writing an email more difficult  in its etiquette than writing a letter?
For a letter it was always
Dear Mr Digge
Or Dearest Rose.
only varying this with the person and their position in  your life.~
As I wrote recently,it appears beginning an email with “Dear John” is considered wrong.Too formal.Dear no longer means anything much.
As in

Dear Mr X

Your execution has been rescheduled and will now be at 3 p,m Friday
Sorry for any inconvenience.
Yours truly
P.Pilate

Also having a greeting at odds with the ending is always a problem

My  own dearest John
I hate you
Worst wishes ever
Anne

When you meet someone in the street it can be the same.

How are you?
I have got  brain cancer
You’re meant to say, I’m fine
I’m terribly sorry.The chemotherapy has affected my mind
Your hair looks  odd.
You’re not meant to say  that
I’m so sorry.You look great.
Excuse me , the ambulance is waiting
Don’t let me get in the way
But you are  in the way
Always moaning, aren’t you? Look on the bright side.
You are blocking the sun
I can’t help where the sun moves to.
OK.Nice to see you
Mutual
See you later.
See you soon
Cheers,old boy
Cheerio