The biggest problem that I faced while dealing with email on iPhone was that it supports one email, contacts, calendar sync at a time. For a user like me who needs corporate and personal email sync, iPhone won’t suffice.
After Google introduced iPhone Sync, I was never practically able to use it coz I was already bounded to my corporate account. Hail, here comes a jailbroken solution with “AddExchange”, which lets you overcome the limitation.
Unfortunately you cannot add a third or more. AddExchange can be found in Cydia from BigBoss repo. After installation, simply click the “plus-button” in the application. Then navigate to Settings > Mail, Contacts, Calendars > SRV2 and add the second account. Works with all 3.x firmware.
Finally, I can use GMail sync without disturbing my work. Jailbreaking rocks.