Formação do Passado em inglês

Hello everyone! My name is Adailton Abreu and I'm a business administration student at University of Pernambuco and my doubt is: Why do I need to use the verb has to form the past in English, mainly in this sentence?

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Why do use has before sent?

Other thing: in the same e-mail, It has the same sentence without the verb has. Look:

Hi Jose!

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Please, this text is it correct?

Thank you a lot!