This article will explain how to create a domain wide Send-as Alias on your domain. This can be useful for when you are moving users to a subdomain.
Step 1:
Navigate to Directory > Users > Explore. Export all your users to a spreadsheet:

Step 3:
Copy and paste the email addresses made by this sheet into the nickname column of the User Directory spreadsheet you already exported from BetterCloud, in column AL:


Step 4:
Import your User Directory spreadsheet back into BetterCloud:

Step 5:
Navigate to Tools > Gmail > Send-As Alias:

Step 6:
Change the second email field to that of your sub-domain, and check 'Make this alias the default Send-As address':
