We have a few items that we list out on the recurring invoice that are based on user count. For example, our helpdesk service is a per user basis. We keep that tied to the Pax8 synced Mailbox counts. We also have some sites that are charged for mail filtering, Ironscales, independent services, etc.
Currently we have some routines to sync these totals but it would be an awesome feature to have an option on the line item qty to LINK to another service. That way the helpdesk service QTY would always tie to the pax8 synced mailbox count.