If you're unsure of the gender of the recipient - always go for the safest 'Dear Sir/Madam'. The person you're writing to will probably reply with more detail about their gender.
Desmond Tutu was a Bishop, so the correct salutation would be, "Your Excellency".
the correct salutation for two men is Messrs
"Dr and Mrs Smith" is the correct salutation. (With Smith replaced with the correct surname)
Many people are unsure of what salutation to use in a letter. Unless you know the person well, it's best to use a formal salutation versus a casual one.
After the salutation of a business letter, the correct punctuation to use is a colon.
Dear ms
madame mayor
Mrs. or Ms.
His Excellency, Ambassador of ................... This salutation can be used when writing to the Forein ambassadors of all countries.
chief counsel
Mr. (name) and (Ms., Miss, or Mrs.) Name
Honorable Consulate