Most commercial email services are not going to get blacklisted: Staying off blacklists is their job. That concern largely only exists with "spin up your own mail" type concerns.
I personally use FastMail, which is a paid provider that I highly recommend to people who value good email service. ProtonMail is really good for privacy, but there's challenges like the lack of normal IMAP support, that can frustrate the average user.
I personally strongly recommend against giving an ad company your data, and could not recommend Google, but it depends on what your friend's values and concerns are.
Note that regardless of the email provider they choose, they should consider buying their own domain and using it as an email alias, so they can easily switch email services later.
I personally use FastMail, which is a paid provider that I highly recommend to people who value good email service. ProtonMail is really good for privacy, but there's challenges like the lack of normal IMAP support, that can frustrate the average user.
I personally strongly recommend against giving an ad company your data, and could not recommend Google, but it depends on what your friend's values and concerns are.
Note that regardless of the email provider they choose, they should consider buying their own domain and using it as an email alias, so they can easily switch email services later.