If you run into an error that says:
This service is not available
Gmail is not available for yesmyown.com. Learn more about Google products you can use with firstname.lastname@example.org.
Did you use this product with a different Google Account? Sign out of your current Google Account and then sign in to the account you want.
The typical solution is to make sure that Gmail is enabled under the Organization & Users Menu and under the submenu “services” … you can access this screen directly if you are now logged into your Google Apps account by modifying this URL:
If you decide to make changes here, don’t forget to save them.
The typical solution may not solve a niche problem that happens when you add several domain aliases to the primary google apps account and you haven’t clicked through the “yes I set up my MX records” validation process. If you added more than one domain to your account, you may also want to check under Domain Settings -> Domain Names:
Make sure that you aren’t missing anything in the domain validation process. You may need to set MX records for alias domains that aren’t the primary domain before you can access Gmail.
Once you have validated everything here, go back to the menu from Step one and disable Gmail, save changes, then re-enable it and save again. Don’t forget to re-enable it, because you will lose email if you leave it disabled for more than 30 days.