Learn Spanish (Spain): Muchas gracias por su atención. Un cordial saludo. - Thank you very much for your attention. Kind regards.

When expressing gratitude, you always use por to indicate the reason or the exchange. Think of it as saying "Thank you in exchange for your attention." Using para here is a very common mistake for English speakers, but gracias para is always incorrect.

Why does the adjective cordial come before the noun saludo instead of after it?

In Spanish, placing an adjective before the noun often makes it sound more subjective, elegant, or formal. In fixed formal greetings and sign-offs like Un cordial saludo or Estimado cliente, the adjective almost always comes first to elevate the professional tone.

Does su in su atención mean "his", "her", or "your" here?

In this context, it means "your" (formal, referring to usted or ustedes). Because this entire pair of sentences is a standard sign-off for a formal email, letter, or business presentation, the formal "your" is the intended meaning.

Could I use this exact phrase to say goodbye to a friend?

No, this is much too formal for a friend. It would sound very stiff, like ending a casual text with "Yours sincerely." For friends or close colleagues, you would use Un abrazo, Besos, or simply Saludos.