2.2.2 Ensure 'Maximum send size: Organization level' is set to '25'

Information

This policy setting limits the size of a message a user can send. Send size includes the header, the message body, and any attachments.

For internal message flow, Exchange Server uses the custom X-MS-Exchange-Organization-OriginalSize message header to record the original message size of the message as it enters the Exchange Server organization. Whenever the message is checked against the specified message size limits, the lower value of the current message size or the original message size header is used. The size of the message can change because of content conversion, encoding, and agent processing.

Rationale:

This setting limits the impact that a malicious user or a system with malware can have on the Exchange infrastructure by restricting the size of outgoing messages.

Impact:

Users will not be able to send a message larger than the limit.

Solution

To implement the recommended state, execute the following PowerShell cmdlet:

Set-TransportConfig -MaxSendSize 25MB

OR

Perform the following actions:

Launch the EAC (Exchange Administrative Center).

Go to 'Mail Flow' on the left and click on the 'Send Connectors' tab.

Click on '...' and select 'Organization Transport Settings'.

Change the Maximum send message size (MB): to 25 and click Save.

Default Value:

10 MB (10,485,760 bytes)

See Also

https://workbench.cisecurity.org/benchmarks/12442

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-5(1)

Plugin: Windows

Control ID: 075945d7d170f537c6493e597732f471259cd596ac78dd9628b46ab0b9eca43d