I use Streak (a YC company, I believe), which has email open tracking built in. It&#x27;s meh... gets the job done, I guess, but it&#x27;s not really their focus. I definitely use it more for the CRM component.<p>Haven&#x27;t heard of RocketBolt. I&#x27;ll check that out.<p>I think Hubspot has something. Was it called Sidekick? I can&#x27;t find anything about it anymore.