Google has changed their SMTP requirements so it is not as straight forward as it once was, to set up SMTP using Gmail in Dash. You now need to create and use an app password.

Create & use app passwords:
Important: To create an app password, you need 2-Step Verification on your Google Account.
If you use 2-Step-Verification and get a "password incorrect" error when you sign in, you can try to use an app password.  
  1. Go to your Google Account.
  2. Select Security.
  3. Under "Signing in to Google," select 2-Step Verification.
  4. At the bottom of the page, select App passwords.
  5. Enter a name that helps you remember where you’ll use the app password.
  6. Select Generate.
  7. To enter the app password, follow the instructions on your screen. The app password is the 16-character code that generates on your device.
  8. Select Done.If you’ve set up 2-Step Verification but can’t find the option to add an app password, it might be because:    Your Google Account has 2-Step Verification set up only for security keys.
  9. You’re logged into a work, school, or another organization account.
  10. Your Google Account has Advanced Protection.Tip: Usually, you’ll need to enter an app password once per app or device

More about this can be found here:

By the way, for meters that are read by Push3 gateways we now have Push3 based triggers. They are meant to replace the Dash triggers so you do not need to keep the Dash software running to have triggers work. You can read more about them here:

To access the SMTP settings in Dash:

  1. Click on the "Events" icon at the top right corner in the main window of Dash
  2. Click the "E-mail" icon on the top of the pop-up window