On Android devices, Gmail is automatically synced with the Gmail server, and vice versa. If you experience problems with syncing, try clearing your phone’s Gmail data and doing a fresh sync with the server.
Just follow these steps:
1. Press your phone’s < Home > button, then press < Menu >.
2. Select Settings and then Applications.
3. Select Manage applications.
4. Select Google Mail Storage and then select Clear data. Answer OK when prompted.
5. Return to the list of applications by pressing the < Back > key.
6. Select Google Mail and then select Clear data. Answer OK when prompted.
7. Restart your phone (Press and hold the < End call > button, then select Power off. Press < End call > to power on).
Your phone will re-sync with the server after restarting (this may take several minutes).
This worked for me, so hopefully it does for you!