Many New Fake Users/ Mail Delivery Failure Notifications

I'm wondering if there's a way to reduce the fake accounts getting registered.

It's starting to fill in my database and makes exporting clumsy. Every day I get a few mail notifications letting me know the emails aren't real or going through but there. Seems to be getting worse every day.

Is there a way to do a sweep to remove accounts without orders? Is there a third party app? Why can they bypass captcha? Too many questions but hoping to get some answers, thank you.

Changes I made today:
- Disabled:
Do not use verification after first valid answer
- Enabled: captcha for login form

Hoping something changes...

Take a look at: Account Activation add-on