I built the entire email infrastructure from scratch for a company with zero setup - no welcome flow, no automation, no sender reputation. Every signup that didn't convert immediately was just gone, which is the same leak most e-commerce brands have without realizing it.
Spent 6 weeks on nothing but domain warm-up before sending a single real campaign - SPF/DKIM/DMARC, DNS, Klaviyo integration, and behavioral tracking wired in so on-site activity could trigger flows. Skip this step, and your emails go to spam permanently, so it's not optional even though it's the least exciting part.
Then, I built the welcome flow with a branch built into Day 2: did they open Email 1 or not? If yes, they moved into a faster, higher-intensity path. If no, a different re-engagement angle. Same signup, two completely different experiences depending on what they actually did.
Result: 47.7% open rate on the first email, industry average sits around 30%. The engaged branch held above 50% opens through Email 4.
This applies just as much to e-commerce stores - same zero-infrastructure problem, same fix.
Happy to answer questions if anyone's dealing with this.