Among the options, DuckDuckGo does not provide email service.

Here's why:

• Gmail: A widely used email service provided by Google. Source
• ProtonMail: An email service focusing on privacy and security. Source
• DuckDuckGo: Primarily a search engine focused on privacy. It offers email privacy features like email protection, but it is not an email *provider*. It offers a service that removes trackers from emails you receive in other inboxes. Source
• Outlook: An email service provided by Microsoft. Source