We’ve had reports from some customers that iOS ActiveSync users are not receiving push notifications of new messages.
We are investigating and hope to have more information shortly.
If you have a non-iOS device with similar issues, please let us know, it could help troubleshooting.
Please feel free to contact support with any questions or if you need assistance.
Update 2015-02-12: I have installed a new build of the ActiveSync server which should resolve this problem.
Update 2015-02-14: After extensive testing we’re considering this resolved, please contact support if you see any further issues.