Problems Using Gmail Accounts
You are a Gmail user and still unable to authenticate your email settings even after trying the other fixes listed above.
Gmail may require you to complete a CAPTCHA challenge if their security system observes “odd” login attempts.
What’s a CAPTCHA?
Some CAPTCHA triggers include:
A user tries and fails to log in too many times (how many is up to Google)
A user signs in from a new geographic location or internet provider for the first time (for example, a coffee shop)
A user has taken steps to overcome the OAuth problem by allowing less secure apps
For any of these reasons, Google may decide it needs you to complete a CAPTCHA in a browser before it can authenticate login. Google wants to be sure that the login is not a hacking attempt by some malicious computer program (bot).
If you want to read more, this page describes this issue pretty well:
• In a browser go to:
• Complete the CAPTCHA
• Retry the “Send Test Email” button in SoftRAID