Add-ons to base Exchange licenses in Prime Portal
To add either Exchange Online Protection, Advanced Threat Protection or Online Archiving, it needs to have a base Exchange online mailbox license such as (Exchange Online Plan 1) in the order for it to process via the Prime portal and also in general.
Please note there are a couple of scenarios:
1) The above applies if the tenant doesn't have any existing base CSP licenses with us or they have Office 365 Exchange mailbox licenses directly through Microsoft.
2) If the tenant already has a base Exchange licence through our CSP program such as Office 365 Business or Exchange Plan 1 already against the tenant, then you don't need to add a base mailbox to the current order in Prime. Just email us and we can manually provision it for you.
Its basically an add-on to a base Exchange license, so the base needs to be present.
Thank you again for your time.