Depending on your requirements, transport limits can be configured in multiple ways. We can configure limits on individual mailboxes, on specific connectors, and even at the organization level. In this recipe, you'll learn how to use the Exchange Management Shell to configure limits based on the total number of acceptable recipients for a message, and also the total maximum size of each message that passes through your organization.
To configure mail flow restrictions for an individual mailbox, use the Set-Mailbox cmdlet as shown next:
Set-Mailbox -Identity dsmith ` -MaxSendSize 10mb ` -MaxReceiveSize 10mb ` -RecipientLimits 100
Here you can see that we've set limits for Dave Smith so that the maximum send and receive size for messages sent to or from his mailbox is limited to 10 megabytes. In addition, the maximum number of recipients that can be addressed when he sends an e-mail message is limited to 100.