Details
You can use this setting to control the total number of message recipients. When a message is first composed, the recipients exist in the To:, Cc:, and Bcc: header fields. When the message is submitted for delivery, the message recipients are converted into RCPT TO: entries in the message envelope. A distribution group is counted as a single recipient during message submission.
Rationale:
This setting somewhat limits the impact that a malicious user or a computer with malware can have on the Exchange infrastructure by restricting the number of recipients for any single message.
Solution
To implement the recommended state, execute the following PowerShell cmdlet:
Set-TransportService -Identity ‘Server01’ -PickupDirectoryMaxRecipientsPerMessage 5000
Supportive Information
The following resource is also helpful.
This security hardening control applies to the following category of controls within NIST 800-53: System and Communications Protection.This control applies to the following type of system Windows.