ActiveSync is important for today mobile device as it allow your mobile device to get up-to-date messages.
By default, Google Apps do not enable the ActiveSync feature alhtough it is supported by Google Apps.
To enable Google Apps ActiveSync from your account,
To Setup your Mobile device,
1. Use your full Google Apps email address as your user name (e.g. “firstname.lastname@example.org”) rather than just your username (e.g “user”)
2. Use “m.google.com” as the Exchange ActiveSync server name.
3. Enable SSL.