Easiest way is the module EmailService. You can find it at https://marketplace.mendix.com/link/component/117934/Tieka/EmailService. No need for you to set up email-accounts and SMTP-services. Just a consumer at service.mendixcloud.com and start sending emails.
In order to send e-mail from your application, you need to connect it somehow to an e-mailprovider.
The easiest way is to import the Email Template module from the Marketplace and configure an SMTP-server like outlook or gmail. Other solutions are custom REST implementations with 3rd party providers.
Please let us know if this helped!