An alias is not a real email address, but just a sort of nickname associated to one or more real email addresses.
So when a customer write to sales@myshop.com, that is an alias, many people receive the same email:
- tony@myshop.com
- sue@assistance.net
- mark@brandanalysis.org
You can create the alias in your provider's webpanel. There, you can also associate it to the real email accounts.
When you set the password for the Super User (that, in my shop, is the main vendor), use the alias.