Mailjet

Mailjet bridges the gap between designer-friendly email editors and developer infrastructure. You can build campaigns visually, but there's also a capable API for sending transactional emails (account confirmations, receipts, notifications) alongside traditional marketing messages. The collaborative tools let teams work together on templates without stepping on each other's work.

Owned by Sinch, the platform combines marketing automation with transactional delivery. It's a good fit if you need both promotional campaigns and critical application notifications in one provider.