Amazon SES

Amazon Simple Email Service launched in January 2011 as one of the more understated AWS products, and it still works the same way today: send a request through the API, an SDK, or SMTP, and SES routes the message and reports back delivery, bounce, and complaint events through SNS. There's no drag-and-drop editor, no contact list feature, and no campaign scheduler built in, since SES assumes you already have an application generating the emails and just need the pipe to send them through. It integrates natively with Lambda, CloudWatch, and the rest of AWS, which is either exactly what a team wants or a sign to look elsewhere.

Pricing is per-email rather than per-contact or per-subscription, and it's the cheapest rate in this list by a wide margin, roughly $0.10 per 1,000 emails sent with no monthly minimum. AWS gives new accounts 3,000 free messages a month for the first twelve months, after which every email is billed, so there's no ongoing free tier the way some competitors offer. Extras add up quickly at scale: a standard dedicated IP runs about $25 a month regardless of volume, and the optional Virtual Deliverability Manager adds roughly $0.07 per 1,000 messages. SES fits teams already running on AWS who have the engineering time to handle authentication, warmup, and monitoring themselves in exchange for the lowest per-email cost available.