Really happy about Gmelius. It really supercharges Gmail for open tracking, follow ups and delayed sending. I really use all of their features. I am eagerly waiting for their app on iOS. One big missing feature is a form of contact management, I use another app for this for now. Only downside is that when you open your browser after a while, all the open notifications are sent one-by-one, they cannot be aggregated, so it can become a little annoying. Other than that I fully recommend this product. Context, I am a single person company and do in-house and remote contracting work. Other, full fledged CRM's just did not fit my bill, especially the sales parts of them. I don't need them and many tools focus on that. Gmelius is the perfect fit for my needs.