If you've just switched your email service to Google Apps for Work, you may want to transfer your Simple Mail email to your new Google Apps for Work inbox. In a few simple steps you can transfer your data from one account to another!
Note: If you haven't set up Google Apps for Work in Apple Mail, please click here
Open Apple Mail and select the emails you would like to transfer to the new account. To select multiple emails hold down the Command (⌘) key, then click the items. To select multiple emails that are listed together, click the first item you want to select, hold down the Shift key, then click the last item
Drag and drop the selected emails into your Google Inbox
Click on the Google Inbox to make sure everything copied over and click Get Mail to synchronize the transferred emails to your webmail account.
You're done! Your emails from Simple Mail should now appear in your Google Apps for Work account (in Apple Mail as well as online in webmail)