Hey Mate @Mateus
I did a test and "Send an Email V2" is capable of sending emails outside the organization.

Please make sure that you are using Exchange Online in your Office 365 tenant and not Exchange servers on-premises. Send an email will only work with Exchange Online. If your tenant turns it off then external mail can't be sent.
At times the email address won't be recognized by the suggestion dropdown, but it won't generate an error and it does send the mail. You just click on the advanced mode icon and add the email.

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