I have tested Polymail on iOS (only) yesterday and today and although it looks nice and has already quite some features which they build since January '16 so respect to them for already creating this so quickly! But there is still a lot of work to do to compete with Spark, Airmail or Outtlook. See also my comparison sheet
here.
These are the main features I'm missing in Polymail for iOS (Alpha):
- Add attachments from cloud storage (e.g. Dropbox) multiple files in one go would be quickest (like Spark)
- Save attachments to the cloud (like Spark)
- Option to show attachments above the email message (like Outlook does)
- Touch ID / password (like Boxer, CloudMagic have)
- Search in archived emails older then two months (like Airmail and Spark)
- Save email as PDF (like Airmail and Spark)
- Snooze to desktop (like Mailbox had)
- Customizable swipe settings (like Airmail and Spark)
- Create multiple signatures (like Spark)
- Task/action list for emails (like Airmail)
- Agenda build in (like Spark, Outlook)
- One tap reply (I read that it's there but couldn't find it in the Alpha version on iOS)
- 3D touch support