Best ESP/email platform to integrate?

What email/ESP extension/platform do you recommend that "plays nice" with nopCommerce? I have been hired to help a small business that has been using nopCommerce for many years but does not use an ESP yet. I have much experience with WordPress/Shopify/Squarespace/Wix but none with nopCommerce. We want to have both automatic transactional emails and also standard batch newsletters, ideally with a user-friendly interface so other team members can get in there and send emails without coding experience. Any solid recommendations for us? Really really appreciate any feedback/direction!

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RE: " has been using nopCommerce for many years"
What version of nopCommerce?

We are on 4.3.

Seems SendInBlue looks like a great option.

MailChimp is the other one to consider.