Push gmail is available for your iPhone, iPod Touch, or Windows Mobile device starting today. It will be a part of an existing google mobile service called Google Sync. With Gmail, the trio of mail, contacts, and calendar is now complete. Please visit the Sync website and follow the link for a list of known limitations. These technical details vary depending on the phone you have.
You might want to know that Sync works using Microsoft® Exchange ActiveSync® protocol. Google reminds you to back up before you set up Google Sync.
For archival and demonstration reasons, here are the details for the iPhone OS as of this writing:
Google Sync for iPhone is still in beta. We're constantly working on improvements, but we've listed below some known limitations of Google Sync for iPhone.
iPhone: All OS Versions* Mail Search and Mail Drafts
Full search capability of your Gmail is not yet available. We don't yet support editable drafts.
*Actions in Gmail
When using Google Sync, certain actions in Gmail may have different behavior than you're used to. For instance, if you "delete" a message from your Inbox, this will actually archive the message. Check out our complete list of how actions taken on your device will affect your Gmail interface.
* Attendee Status for Calendar Events
The iPhone doesn't reflect the attendee status (Yes/No/Maybe) of guests in the user interface of the Calendar application. Google Sync provides a hint in the form of a checkmark in front of a guest's first name.
* Imported Recurring Events May Not Sync
If you've imported calendar entries from another calendar system into Google Calendar, you may find that only the first occurrence of the event is synchronized, or - in some cases - the event may not be synchronized at all. Events which occur multiple times per month (for example "the first and last Monday of each month") cannot be accurately represented in the ActiveSync protocol. Recurring events created within Google Calendar will sync correctly.
* Limited Contact Information
The iPhone can synchronize up to 3 email address. Phone number synchronization is limited to 2 Home numbers, 1 Home Fax, 1 Mobile, 1 Pager, 3 Work (one will be labeled 'Company Main') and one Work Fax number.
* Apps Administrators: Learn how to enable Sync for your domain.
iPhone OS 3.0 Only* Adding / Editing Attendees on the iPhone Doesn't Work As Expected
When you create a new event on your iPhone and invite other attendees, the event will appear on their Google Calendar, but they won't receive an invitation by email. If you attempt to edit the attendees of an existing event on the phone, you may receive an error message about invalid email addresses and the event may not be updated correctly. We recommend using the web interface at http://calendar.google.com to add or edit attendees at this time.iPhone OS 2.2.x Only
Note: Google Sync is only supported on iPhone OS versions 3.0 and above. Please upgrade before setting up Google Sync.* Limited to 5 Calendars
Syncing more than 5 Calendars to the iPhone's Calendar application often causes all Calendars to appear in the same bright yellow or cyan color, making it impossible to use the Calendar application effectively. Google is working with Apple to resolve this issue.
* Modified Instances of Recurring Events Not Always Deleted
In some cases, the iPhone doesn't respond correctly to change requests for individual instances of recurring Calendar events and creates duplicates of these events. This problem often affects events created in the GMT timezone when the series of events spans a Daylight Savings Time boundary.
Example: If a series of recurring events is created in August and a change is made to an instance of the series in December, the iPhone will show both the orginal event and the changed instance in the Calendar application.
* Modified Instances of Recurring Events Not Removed When Declined or Deleted
When an event is declined or deleted by an attendee in Google Calendar, the instance is removed from the attendee's Calendar on the iPhone. However, if the event is a modified instance of a series of recurring events, the iPhone doesn't respond to the delete command and the declined event remains on the device Calendar.
Your mileage may vary depending on the device you are on.