Ask HN: Reply.io Alternative with Strong API?

I'm trying to create a cold email outreach sales funnel, but I want to keep the data in my own datawarehouse. I want to send emails and track whether the recipient has opened the email and clicked on the link.

I like Reply.io, but I cannot find an easy way to track campaign results per participants. I've looked into sending using Google Mail API, but tracking the open rate and click rate becomes a bit more cumbersome.

Any suggestions?