All I get is SMTP connect() failed.

Are you sure that port 465 is open on your WordPress site?

You have two options

1. Switch to OAuth 2.0 instead of Password authentication OR
2. Use Password authentication but enable:

1. App-specific passwords or
2. Two-factor authentication
3. and Enable less-secure apps on your Google account

See https://googleonlinesecurity.blogspot.ca/2014/04/new-security-measures-will-affect-older.html

Actually I had to go here:

https://www.google.com/settings/security/lesssecureapps

And turn On Access for less secure apps (See this screen-capture)

That’s what I said (#2-3)

If anyone else comes here looking for this answer, users of Google Apps for Work or Google Apps (Legacy), beware that Google no longer permits them to “enable access for less-secure apps” and they will have to use OAuth 2.0. (See this screen-capture)

It still strange as my Newsletter plugin has its own SMTP configuration setup and it worked without me having to turn On Access for less secure apps… any idea why?

Just because your newsletter works today doesn’t mean it will still work tomorrow. Google is slowly migrating all users to the OAuth 2.0 security model as per here and here.

I got hit in January.

How would one setup OAuth 2.0 authentication?

Do you know of a well documented (EASY) guide that specific to your plugin?

BTW; thanks for all your help and for responding so fast!

Search the WordPress plugin repo for OAuth2

Awesome; thanks!