What is the treatment for university professors?

[Mon]

I need to write a formal letter to a university proffesor and a doctor, how can I start? Dear Sir/Madam? No idea.

Thank you for your help.

[Soup]

Dear Professor <name>,

Dear Dr <name>,

[BobK]

Incidentally, tratamiento is a false friend here. You would ask 'What is the right way to address...?'

b