I've been running SmarterMail as a virtual server for many years. My physical server is an HP Proliant running Windows 2012 R2 and Hyper-V. SmarterMail is running on a Windows 2012 R2 virtual machine. Let me list just a few of the advantages.
1:) Live Migration to another server with no downtime.
2.) The ability to make a snapshot (checkpoint) at any time and then revert to it quickly with a few mouse clicks. This is a great feature to have before a major upgrade.
3.) Backup and restore without having to turn off/reboot physical server
4.) Easy to add/expand/shrink storage with no downtime.
5.) Add memory or cpu resources from the Hyper-V console, all it takes is a quick VM reboot.
6.) Real time replication/mirroring to a second server, built in to the OS at the Hyper-V level, whether local or at another hosting facility for serious redundancy.
7.) Create and manage virtual switches and virtual LANs from the Windows Hyper-V console.
8.) All of this is included in one Windows 2012 R2 license.
I just couldn't fathom going back to a physical server as an application server for love nor money!