You can manage your custom Google Email account with a Highwire registered domain.
To do this the MX Records for Google Email will need to be setup in Highwire.
In Highwire, go to Settings>Domain Hosting.
For the domain registered in Highwire, click the Pencil icon to open the DNS/Email Settings.
Enter the values as shown in the image below then click the Save DNS button.
Here is a link on how to get started with Google: