Suddenly all emails unread marked

Hello,

we have got a small problem with some user dbs.

Over night, all emails in the db from three users are completly unread.

This problem have happend the second time.

I can´t explain why.

Server version: 8.0.2 FP4

Client version: 8.0.2 FP4

How can that be?

And only by three users, not the rest?

No agent is running, programm or task.

Any idea, where i can look or what i can do?

Thanks for help

Bye