Hi @Marco_Saad
First of all welcome to the community!
In order to be able to open the email in Outlook before sending, you only need to set Open email before sending flag to Yes. You can find this flag in Docentric Print destination settings > Email and below the Subject field as it can be seen from the screenshot:
Now when you execute the report, you will get .eml file downloaded and you can use Outlook to preview it before sending.
If you need any additional help, feel free to reach out.
Best regards,
Semir