I know that you can track whether a user has viewed an email with a 1px image; are there other ways too? Since a lot of email clients have been blocking external images for a long time, I figure either the quality of the metric must be pretty bad these days or a better method has emerged. Preferably the latter so I can learn something new :)
It's really nice for services that don't use newsletter companies or 3rd party mail services. E.g. at Notifo, we are using our own mailservers to send notification emails, and now we don't have to build our own analytics backend. We've been using the Mixpanel solution since their beta phase, and we've been very happy with it so far.
Mixpanel just improved already-impressive analytics product. Email tracking is a lot like realtime web tracking, and to the best of my knowledge, realtime web tracking is something mixpanel has done very well so far.
From a business perspective, mixpanel is now also competing in the email analytics space. That's perfect for at least two types of customers. It's good for the customer who uses mixpanel for website tracking and wants to expand into email analytics. It's also great for the customer who is looking for an analytics service that does email tracking as a part of its service offering.
It's always nice to get more value from fewer products. It's like making a few tweaks to functions to make them do more. Less work, less code, more value. It's better than getting a new service each time a new use-case (like email tracking) arises. I think mixpanel understands this. Mixpanel is evolving into an end-to-end analytics service -- that's the extra value I see here.
We have switched ESPs 3 times since our startup launched... it would have been great to have all the data on a service like mixpanel instead of starting over each time. On top of that, we also use a mix of ESPs and our own mail servers from time to time, so mixpanel's service would help there as well to consolidate everything.
If you are running a lot of different types of offers or campaigns other than just email it can be nice to have all of your stats in one place. I can't think of any other reason to use this over the tracking provided by any of the ESPs out there.
When techcrunch writes about your startup, not only do they give you a link for your company site, but they also give you a SEO specific link "email analytics" which will pay a lot of dividends in the future.