You can reduce your administrative work for domain alignment by delegating your subdomain to Inxmail, see Scenario 1 – Authentication and domain alignment (with domain delegation).
If you opt for domain delegation, you only need to store so-called NS entries once with your ISP in the Domain Name System. Inxmail takes care of everything else for you, such as the recurring maintenance of the DKIM keys.
Note: Domain delegation refers exclusively to the respective subdomain and not to your main domain.
