I use Streak (a YC company, I believe), which has email open tracking built in. It's meh... gets the job done, I guess, but it's not really their focus. I defin

I use Streak (a YC company, I believe), which has email open tracking built in. It's meh... gets the job done, I guess, but it's not really their focus. I definitely use it more for the CRM component. Haven't heard of RocketBolt. I'll check that out. I think Hubspot has something. Was it called Sidekick? I can't find anything about it anymore.