I just saw this appear the other day on my Exchange Server., I did some research and found out that it has to do with IIS and smtp.
Event Type: Warning
Event Source: W3SVC-WP
Event Category: None
Event ID: 2273
Time: 12:58:24 AM
Worker process could not access metabase due to disconnection error. Marking process as unhealthy.
Does anyone have anymore information on the message?