Note : I am using Google email (i.e. Gmail ) account to send emails.

1. Create a Reactive Application add screen in it.

2. Add Email by right clicking on email shown below image ate step 1

3. Add Message to send in email ,here you can customize message using expressions and Data from Entities.

Refer below screen to accept email and Create action on button click to send email.

On Clicking Send mail button add action below, Note that send mail action in below image is server action because Email widget can be used Only in Server Actions. 

Check the below image for how email widget is configured and an Email Bock which we have created in First Screen above.

After this we need to Configure Service Centre for sending emails.

1. Open your service center

2. Go to Administration -> Email

3. Do changes as per below image

    1. User Name - Enter your Outsystems Email ID here.

    2. Default Sender Email - Enter your Outsystems Email ID here again.

    3. Add Default Sender Name here that can be your or organization name.

    4. Redirect Emails To Test List: Tick only if you want to redirect emails else don't.

        Test List Addresses: Enter email lD to redirect emails

    5. Save and Apply Changes

Now Configure your Gmail for sending emails 

Email configuration:

1. Go to your Email settings/smtp server account setting--->

Make following changes:

a) Enable IMAP service. Refer Below Image

b) Go to account setting-->Go to security settings--->Disable 2 Step verification

c) Allow access to less secure app. Refer Below Image

  1. Click on Your Account Initials Right to corner

    2. Click on Security 

    3. Enable access to less secure Apps

2. Go to the link--->https://accounts.google.com/DisplayUnlockCaptcha

click on the continue button and it will allow your new application to accessed from this smtp account.

And that's Done.

Please feel free if you have any doubt in this.

All the Best.