Migrating a client from FuseMail hosted Exchange to Office 365. Unfortunately, FuseMail has no administrative controls, and the client only has 8 user accounts, so I've fired up some virtual machines and installed Windows 10 Pro along with Outlook 2016 and connected each of the accounts to their own individual Outlook client. I configured each and every client to cache ALL data from the server, yet I see massive discrepancies in the OST compared to the Mailbox size in the admin panel for Fusemail. I understand these numbers can be different, but for example, I have a user that has 32 GB of account data in FuseMail, however the current OST size after all folders are up-to-date ticks in at a measly 3 GB.
Alarmed, I compared the earliest email data on the Outlook client to that of OWA in this particular account, I scrolled down to the bottom of the Inbox and to my dismay, noticed that there was a "There are more items in this folder on the server" message. I double-checked the configuration of the Outlook client and verified that it is indeed set to cache ALL data (as opposed to 1 year, 6 months, etc). I then noticed that ALL of the Outlook clients are the same -- single-digit OST files in the GB, whereas double-digit mailbox data for the same respective account on the server. In addition, even after clicking the "Show More Results" link, the oldest message I can find in the Outlook client is 2 years old, whereas in OWA on the server, the oldest message is 4 years old!
I want to move this data as efficiently as possible. Is there any way to configure Outlook to force it to download ALL data to the OST so I can export it to PST for the migration? Could this be a limitation coming from the FuseMail Exchange host somehow?
Any help would be greatly appreciated.