I raised this last year and the topic was closed as Z-Push was considered abandoned, but infact the Z-Push project has been quite active and supporting all the latest iOS releases etc.
If anyone has successfully incorporated Z-Push into Hestia and mail i would be very appreciative on a guide and willing to donate for your time.
FYI, Z-Push gives you real time email notifications rather than having to schedule email sync when using a mobile email client, but I am sure you already know that. It would definately help in moving away from Gmail / hotmail / etc so that you can completely have an equivalent independent email service.