Postman SMTP on "Unable to send emails from WordPress"

Hi Amy. You're doing good. And when you go out tomorrow night you can tell all your friends how you wrangled Yahoo into creating OAuth 2.0 authentication credentials for your website. People will buy you drinks.

From the FAQ, here are the instructions to get your Yahoo Consumer Key and Consumer Secret.

How do I get a Yahoo Client ID? (For Yahoo Mail users only!)

1. Go to Yahoo Developer Network and select 'Create an App'.
2. In the 'Application Name' field enter 'Postman SMTP'. For 'Application Type' choose 'Web Application'. In description write the name of your WordPress site.
3. In 'Home Page URL', enter the 'Home Page URL' shown on Postman's Settings page.
4. In 'Callback Domain', enter the 'Callback Domain' given by Postman - remove the trailing slash!.
5. Under 'API Permissions' choose 'Mail' and under 'Mail' choose 'Read/Write'
6. Click 'Create App'
7. Enter the Client ID and Client Secret: displayed here into Postman's settings page.