google-appsgoogle-calendargoogle-drive
Ive got a @gmail / @googlemail email account that i also use for google drive, google calendar etc..
I would like to update / transfer my google account username to a custom domain eg. sam@mysite.com instead of sam@gmail.com.
I would still like to keep my @gmail email address, but not use it as the username i use to login to google drive / calendar etc.
Is this possible ? If so how would i do it ?
No, you can't do that.
Alternatives: Either you find some other free mail service like outlook.com for your domain, or you create a mailbox elsewhere and forward to your Gmail inbox. Sending from your Gmail account under a different address is possible because you can set SMTP to a different provider in the Gmail settings.
Reason: If you want to use your own domain with free gmail, you have to create the email address and mailbox elsewhere and then forward those emails to your Google inbox or access them through POP3.
Simply pointing your MX to Google does nothing because Gmail is not set up to receive mails directed at your domain. It takes both: Setting the MX records and letting Google know that it is the recipient of your MX records. This is what you do in the Google Apps Control Panel when you sign on with your domain.
Since Google won't let you do that with a standard Gmail account, it's not possible.
As of sometime in 2014 you can migrate emails using the Data Migration tool in the Admin console. This is meant for transferring data between domains, but you can use it to transfer data within your domain as well.
Before you start, you may want to log in as the source user and apply a label to all of their emails. Otherwise, they will just be thrown in the target inbox with just their existing labels, which can be hard to sort through. While you're there, grab an application-specific password if you have two-step verification turned on.
Best Answer
I have multiple accounts for various items, including domains. You can just start using the new account and still keep the old one. If you wish, share access to Calendar and folders until you are completely moved over. I am logged into multiple accounts at one time in the same browser. So basically, if you want to keep the accounts, there is no reason not to and no reason to feel you need to log into one only.
That said, if you really want to move things, there are a few options with varying degrees of success.
If your custom domain is a G Suite domain, see the instructions here for transferring various types of data or these for moving large amounts of data. These may require you have admin access to the account. There are a couple options in the Marketplace to transfer some items.
The Takeout utility is reportedly not very good for getting things back into the new account.