Brevo

Brevo combines marketing automation with a solid transactional email service via REST API. You get 300 free emails daily, which covers most startups' transactional volume (receipts, verifications, notifications) without cost. Their single dashboard handles both marketing campaigns and transactional sends.

Good for small to mid-sized teams that want one platform for all email. Brevo works well if you're already using them for marketing campaigns and need the same vendor for transactional sends, or if you're under their free tier and don't need separate routing.