In late 2015, Microsoft announced plans to cut the amount of free OneDrive storage to 5GB and end unlimited storage for Office 365 users. The cutoff for unlimited users was set for yesterday, March 1, which means that unlimited users should now start seeing their unlimited storage dropping down to 1TB.
In an explanation to Neowin, Microsoft noted that the changes may take up to 48 hours to become visible to unlimited users. If you happen to still have more than 1TB of files in your OneDrive, then your account will move into what's called "over quota mode," which gives you 3 months to get below that 1TB threshold. If you miss that deadline, your account will be locked down 6 months, at which point you can request 30 days to access your files again to move below 1TB.
The move to limit OneDrive storage after initially offering unlimited space to Office 365 users has received plenty of backlash. However, in its original explanation, Microsoft said that it made the decision based on some subscribers using excessive amount — up to 75TB — of storage. As part of the changes, free storage has already dropped from 15GB to 5GB, and Microsoft no longer offers 100GB or 200GB plans.