This blog post might seems a little old but still cover the topic very well.
Please, read the comments contributed by readers at the bottom.
If I find more updated article, you know what I will do and where you can find it. Until then
“Which Transactional Email Service is the Best? Mandrill vs. Sendgrid & More”
https://www.ventureharbour.com/transactional-email-service-best-mandrill-vs-sendgrid-vs-mailjet/
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