Nightly DB Quota OK Mails

I am getting this mail each night for several databases (and also customers are getting this Mails for their DBs as long as it is enabled on the corresponding server) There are no ERROR/BAD-Messages only GOODs. Further it does not matter if it is unlimited or set to a quota. Happening on RC1 as well as stable-3.1 from friday.

Der belegte Speicherplatz Ihrer Datenbank z_c3_rcwebmail ist wieder ok.
Datenbank:                        z_c3_rcwebmail
Belegter Speicherplatz:            2.08 MB
Verfuegbarer Speicherplatz:        0 MB
Belegter Speicherplatz in %:    0.00%