Set Up Gmail, Google Calendar, and Google Contacts on iOS

Settings-> "Mail, Contacts, Calendars"->"Add Account->Microsoft Exchange (NOT Gmail)

Email          : [use gmail email address]
Server        : m.google.com
Domain      : [leave the Domain field blank]
Username   : [use full gmail email address]
Password   : [use gmail password]
Description : [use any description]

(If error encountered ie "Unable to Verify Certificate", just tap cancel).
Enable Mail, Contact, and Calendar syncing from the account settings by turning ON feature.

iOS 4 and Google Sync via MS Exchange ActiveSync Sending Error

Started getting "Cannot Send Mail : An error occurred while delivering this message." on iOS 4. To solve this just go to

Setting->Mail, Contacts and Calendars->Select Account->Account Info->Use SSL->OFF->Done

then

Setting->Mail, Contacts and Calendars->Select Account->Account Info->Use SSL->ON->Done