“Sehr geerhte” vs “Sehr verehrten”

Hi
When should you write “Sehr geerhte” vs “Sehr verehrten”?
And do you use both for speaking and writing?
 

Hi RexV, 

Sehr geehrte Damen und Herren is the German go-to greeting in a formal letter, sort of like "Dear Sir or Madam" in English.

Meine sehr verehrten Damen und Herren is a phrase that you would use as a formal greeting in a public speech.

I hope that clears it up for you!

Grüße, 
Leah von Rocket German