Once you provision your primary domain on Vaultastic for archiving, you need to enable the Auto User Creation property of your domain. Users will be created automatically as soon as an email is received to the Vaultastic domain.
Assume, Amit and Neeta are users of the domain baya.in.
This domain has been provisioned on Vaultastic with the Auto User Creation property of the domain enabled.
When Amit sends an email to Neeta from his primary domain, a copy of the email is archived on his corresponding Vaultastic accounts of Amit and Neeta on Vaultastic. As the copy is received to Vaultastic, the system creates users Amit and Neeta on the Vaultastic domain.