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Google Apps for domain using CPANEL

http://www.google.com/apps/intl/en/group/index.html

Configuring Your MX Records: cPanel

1. Log in to your cPanel account.
2. Click Mail.
3. Click Modify Mail Exchanger (MX Entry). A list of your current MX records will appear.
4. Click Change an MX Entry.
5. In the Change MX for… field, enter ASPMX.L.GOOGLE.COM.
6. Click Change.

Congratulations! Your MX records are now configured to point to Google. Keep in mind that changes to MX records may take up to 48 hours to take effect.

Source: Google Help