You can import historical mail data only for users subscribing to the TRACER, DURABILITY or HOLD plan. Mithi provides access to a DIY portal to help you import data into these vaults. For all the historical data that you upload into the vaults of Tracer or Durability users, you are charged at per GB per year as the holding price for upfront upload. For the HOLD plan you may upload any amount of historical data, limited only to your purchased storage volume for the HOLD plan.
In addition for every GB you import into any of the 3 plans, you are charged a one time migration cost of per GB to cover resource usage cost in copying, converting and indexing the data.
E.g. One DURABILITY user needs to import 15 GB of historical data. There will be a recurring annual charge for 15 GB at the rate of /GB/year and one time migration charges of 15 GB x per GB.