The requirement is to enable monitoring which triggers an alert as soon the email count in the Inbox folder reaches 200. We have 4 mailboxes for an application where the emails are processed.
Release : 8.51
Component : UIM - EXCHANGE_MONITOR
At this time, it is not possible to monitor the mail count in a mailbox using the UIM Exchange Monitor probe. We rely on perfmon counters for many metrics and there does not seem to be a counter provided by Microsoft for this.
However, it may be possible to run a PowerShell command to get that value: