OptinMonster optin forms has many different types to help you capture customer emails: popup forms, floating header and footer bars, slide-ins or sidebar forms.

They have exit-intent technology as the key feature to prevent site abandonment. With their easy-to-use popup builder, you can quickly tweak and customize the design within a few seconds to produce the best design for your site. Here's the example of well-timed designed exit intent popup right in their website as a live demo for potential customers:

Pricing: From $9 to $29 / month, but billed annually only

Install: Popups by OptinMonster