You can use your gmail account to send emails. However, Gmail will block your Mendix app until you turn on the “Allow Less Secure Apps” setting.
You could use your own mail, as Monali said. Alternatively, what I’ve found useful is Papercut. It’s an smtp that’s free and pretty easy to use. https://github.com/ChangemakerStudios/Papercut-SMTP At the bottom of this page there is a link to the installer.
This works wonderfully when set up correctly, as it 'catches’ the mail you send from your application and means you don't have to worry about gmail blocking your app. In the software there are tips on how to configure your mendix setup, but the main things to note are that the server needs to be your localhost and the port number for Papercut is 25.
I hope this helps!
You can set a constant ISLOCAL with true/false. If true, send email to test mailbox. Otherwise, send email to the real address. Advantage is that you don’t need an extra party. But, I don’t suggest this option, because I think it’s not OK to have constants only for testing purposes.
In my own situation, I always use https://mailtrap.io. This is not only for catching all e-mails, but also to view mails like different clients (browser, mobile, etc). I don’t know Papercut, but it’s maybe comparable. You can also use different ports, useful if port 25 is blocked.