Does anyone have any advice on email verification services?

I'm looking for something where my interns can do single email checks and I can do bulk checks. The idea would be to use this tool to double check guessed owner emails (ex: John Doe owns, check if is a valid email address) as well as double check entire lists before uploading to an email sequencing tool.

I'm currently looking at the below options. Would love to know if anyone has any experience with these or any other tools that they like!: