I use Polymail on Mac and IOS and the email tracking feature works well on both
I asked a similar question a week back, only to realize that Polymail was already installed on Mac long back. Polymail offers read-receipts even without Polymail Pro subscription.
I've been using Newton for a about 2 months now, and love all the features they have in addition to tracking. Great design, has features such as tracking, snoozing, send later, as well as integrations with other tools (Trello, Wunderlist, Pocket, Evernote, Asana, Todoist etc.)
Amazing email client and awesome tracking. Highly recommend.
If you like Mac Mail this is an extension with some features that includes tracker. Very happy with it, paid the full software for unlimited actions
Tried Polymail, Newton, Spark, Airmail and some others. When Astro came along, I stuck with it. They still don’t support IMAP and may lack some other fancy features, but the current featureset (priority box, snoozing, tracking, follow up reminders, inline answering etc) is well executed and reliable.
Been using this after my Polymail trial expired. Love the simplicity and simple AI features (You haven't been opening emails from , should I auto-archive and mark future messages as read.?) Best alternative if you are looking for Mail Tracking, Scheduling and some intelligence, the Priority inbox is A+ too
Seamless integration into Gmail through Chrome and works on all types of computers. Offers a reliable email tracking feature as well as a bunch of other features.
Mixmax also has a desktop app – weak spot is mobile, but supposedly in the works. Very much a desktop tool at the moment, but our team uses and loves it.