Some webhosts require SMTP to be setup to send emails from WordPress. The first time you setup SMTP, follow the directions here to properly configure your Google Account. On future websites you setup, you can simply follow these instructions.
- Install the gMail SMTP plugin by naa986
- Login to console.developers.google.com
- Go to credentials > create credentials > OAuth Client ID
- Select the web application option
- Give it a name, include both the http and https version for the origin, and the redirect URI can be found in the gMail SMTP WordPress plugin
- Copy the client ID and Secret to the gMail SMTP plugin
- Finish filling out the plugin settings then go to the test tab, and make sure everything works. Troubleshooting help can be found on this page.