Gomez de Cordoba (or Gómez de Córdoba) is what we name "apellidos compuestos" it means it is a single surname. Surely the person has another surname. It is also common a person has two names. For instance: Miguel Antel De la Riva De la Torre 1st name: Miguel 2nd name: Angel 1st surname: De la Riva 2nd surname: De la Torre In a formal email I would write: dear Mr. De la Riva

Mr. Gomez de Cordoba. This would be considered one last name in English. Be sure to put a period after the title "Mr." and capitalize the "g" in Gomez and the "c" in Cordoba. If he specifically asks you to call him by something else, then that is when you would refer to him by what he has requested of you.

It would be fine if you say "Mr Tom Gómez de Córdoba", but if you want to skip the name and just say the surname, you should use the first surname (at least that's the usual), not both, nor the second, just the first surname. And to your other question "Mr Gómez" is fine, you don't need any other capital letter but the initial. Hope this can help you :)

If you are speaking in English you would use the last surname, unless you are told differently by that person. Because the example you gave is difficult because it has "de" and in that case i would say Mr. Gomez de Cordoba. If it didnt have de I would say Mr. Cordoba.