To be honest, I'm not really sure what's going on. There are virtual disks in the log file which do not exist (according to the screenshot), and I'm not talking about the second mailserver.vmdk which is located on another datastore. I'm talking about "mailserver_1.vmdk" which is configured as "independent-persistent" (i.e. should be exluded from snapshots, but there is one), and "mailserver_5.vmdk" which replaces "mailserver_1.vmdk" on "scsi0:1" by Hot-Removing/Hot-Adding the virtual disk (shown at the end of the logfile).
Maybe it will help to run RVTools to find out whether there are files which might be osolete (marked as "zomies" in RVTool's output.)
André