How do you build email automations for your projects/startups?

Hi y'all!

I'd like to implement an email automation for my app so that, for instance, new users get a "welcome" email and those that don't finish making an account get an "almost there" email — in the future, I'd like to send out different emails based on possibly more complex user events (e.g. if a user hasn't been active for x time and has done action y then send contents z, etc.).

Currently, I'm sending out emails manually based on new users I'm getting on my platform.

A quick search shows Braze, CleverTap, and Emarsys do this type of data-driven communications stuff but it's clearly for the enterprise-level since there's no sign-up and you have to talk to sales.

I wanted to ask how you guys have done this and/or how you'd go about doing this?