Iphone push email on directadmin

[jca]

Hi, some of my clients lately have bought iphone's, and started to ask me about the possibility of offering push email. I've been looking around for an alternative and so far my findings show that the only way to make it work from the server is Zarafa; as all the others rely on other their own servers to do the pushing.

Anybody has it running with Directadmin? Is it compatible? Any other alternative?

Thanks

Jose