Someone got this mail too?
What does that mean?
it means that all files not downloaded since 7 days will be deleted (in few days) - (if you have already received an such email few weeks ago, files will be removed tomorrow).
As you know Uptobox.com is not a cold storage (=files never-downloaded) service. That's mean Uptobox use powerfull dedicated servers and hard disks drive to provide best service quality (for example download and upload speed).
This service quality cost a lot of money (CPU,RAM, HDD, SSD, data redundancy, powerfull fiber network, electricity).
Uptobox storage is unlimited, but only if you are not using most of this space with files never downloaded (= cold storage).
Your account is using 6TB of space, and generated only 0.0110 Uptobox premium point last month. This is unfortunalty not enough to guarantee our service quality with low premium price.
What I can do?
You can reduce the space used by your account by deleted old useless files, or you can also share more of them with your friends to earn more premium points.
Is this permanent ?
Until you download ratio is low, yes.