Postmark

Postmark sends one kind of email only, the receipts, password resets, and account notifications your app triggers automatically, and it deliberately doesn't offer bulk marketing sends on the same infrastructure. That separation is the whole pitch: mixing a newsletter blast with your password-reset emails on shared IPs can tank inbox placement for both, so Postmark's Message Streams keep transactional and broadcast mail apart even within one account. The API and SMTP integration are simple to wire up, templates support variables and layouts, and the activity log shows opens, bounces, and spam complaints for every message down to the exact timestamp.

Pricing bills by email volume, not by any contact list, since there's no list here to begin with. Paid plans start at 10,000 emails a month with overage priced per additional thousand, and a free developer plan caps out at 100 emails a month with no expiration, useful for testing but not for production traffic. Inbound email parsing and a few other features sit behind the higher tiers. Postmark is the reference point for deliverability reputation in this category and it's the right call for a team that treats every failed password-reset email as a support ticket waiting to happen.