I have two users that have Problems. One gets crashes and another one has a very slow Client, especially when creating new Folders or moving Folders.

So far, I did a structural rebuild and an "Analyse/Fix databases" on the user database (checked all Options), with no effect.
Now I would do an "Analyse/Fix databases" for the message database, too. But I have never seen a how-to for this, they all say, uncheck the message database. So why is that? Is it dangerous to do that for the message database?

For one user, I also did a recreation the user database, again, no effect. So I guess it must have sth. to do with the message database.