Is it ever good practice to separate website hosting from email hosting for a single domain, via virtualization?

Example:

A dedicated server hosts a single domain, xyz.com

This server runs a web application, which is publicly available via xyz.com

The server also hosts xyz.com IMAP email accounts.

Two VPSs could be set up on the dedicated server - one for hosting the web application, and one for the email accounts. This would presumably safeguard the email accounts from any potential problems derived from the web application.

Is this done much in practice, and if so what is the best method of going about this? I was thinking Virtuozzo + Plesk. However my problem with this approach is the disconnect between the two control panels. It would be ideal to set up the domain in a single location which took effect in both virtual environments.