One Virtual drive filling automatically

Dear Experts,

We are using Microsoft Exchange 2013 in a Virtual Windows Server 2012 R2. We have different Mail box data base storage. Among them one of the Drive for STD-Mailbox space is gradually filling. Bellow warning is showing in vRealize Operations Manager.

"One or more guest file systems of the virtual machine are running out of disk space. Check the symptom details to identify the affected guest file system".

Kindly advice how stop.

Thanks a lot.

Regards,

Anis.