more intelligent email marketing flow/autoresponder providers/SAAS -- Drip, Klaviyo, ConvertKit, Customer.io etc have ALL grown hugely over the past few years. If you bootstrapped a half-decent business in this space you probably became successful.

Yeah, right now it is all about email marketing automation. Few years ago, the hot space was project management software and before that it was bug tracking software. Get your timing right and you are golden, start too early or too late and you will be in a tough space.

Thanks for the explanation. My guess is it takes effort to find a good niche/space to start a business. Many a times people never know if a space will be successful a few years later.

from looking at the article they look like a/b testing tools.