After you setup your account at google, it asks you to prove you own the domain. Choose the option to upload an html file and follow the instructions for that. Then, setup the mail using the "mx records" options. Google doesn't list how to do it for X10, so choose the generic option. It should be something like this:
SOMETHING.GOOGLE.COM.............10
SOMETHINGELSE.GOOGLE.COM.....20
ANOTHER.GOOGLE.COM.................20
BLAHBLAH.GOOGLE.COM................20
Go to cPanel->Mail->MX entry. Edit your level 0 to be the same as the lowest number (in the example SOMETHING.GOOGLE.COM) Type it exactly as you see it. Don't use a period at the end of ".COM" Keep adding MX records until you have them all put in. cPanel doesn't let you do more than one entry per level, so you must go in order (0,1,2,3,4, etc) and not (0,1,2,2,2,2,3, etc) Order is really pretty irrelevant, just do it in the order they appear in google. Then, tell google to verify the records (it'll take a while, maybe a day or two)
If google has a problem and doesn't work after 48 hours, check your domain here:
http://www.mxtoolbox.com/
and if the test doesn't match your cPanel, submit a ticket:
http://support.x10hosting.com
for whatever reason, it seems like cPanel doesn't like to change the MX records for you sometimes and you have to ask an admin to force it.
So, that's what I've done before. Have fun
