As of now, Mixmax only tracks emails sent from desktop Gmail. If you do send someone a tracked email with Mixmax and they respond from their mobile phone, tracking on your end will still work. That is, you'll be able to look at your Mixmax Live Feed (when on your laptop/desktop) and see the information about tracking.
Got any ideas for which features we should prioritize? Get in touch and let us know — send an email over to [email protected].