Using the Exchange Shell to Track Failed Message Delivery

http://social.technet.microsoft.com/Forums/en-US/exchangesvrgeneral/thread/9c44d4aa-cf81-47dd-ba38-c28171c750e2/

http://serverfault.com/questions/19568/how-do-i-change-the-max-attachment-size-in-exchange-2007

https://rajisubramanian.wordpress.com/2014/01/26/exchange-server-2013-message-size-configuration-detail/

http://exchangepedia.com/2007/09/exchange-server-2007-setting-message-size-limits.html

http://abbottprime.com/blog/Exchange2007AllowingLargeMessages.aspx

https://technet.microsoft.com/en-us/library/bb124708(v=exchg.150).aspx

Show per-user limits:

Get-Mailbox | Select DisplayName,RecipientLimits

Transport:

Get-TransportConfig | fl max*

Set-TransportConfig -MaxDumpsterSizePerStorageGroup 40MB -MaxDumpsterTime 07.00:00:00
Set-TransportConfig -MaxSendSize 30MB
Set-TransportConfig -MaxReceiveSize 30MB

Send connectors:

Get-SendConnector | select identity,maxmessagesize

Set-SendConnector -Identity 'Your Identity' -MaxMessageSize 30MB

Receive connectors:

Get-ReceiveConnector | select identity,maxmessagesize

Set-ReceiveConnector -Identity 'Your Identity' -MaxMessageSize 30MB

Start the Exchange Management Shell as an administrator:

Get-TransportConfig | fl max*
Get-ReceiveConnector | select identity,maxmessagesize
Get-SendConnector | select identity,maxmessagesize

Set-TransportConfig -InternalDsnMaxMessageAttachSize 20MB
Set-TransportConfig -MaxReceiveSize 20MB -MaxSendSize 20MB
Set-TransportConfig -MaxDumpsterSizePerDatabase 30MB -MaxDumpsterTime 07.00:00:00

Set-ReceiveConnector "Windows SBS Internet Receive HACSVR" -MaxMessageSize 20Mb 
Set-SendConnector "Windows SBS Internet Send HACSVR" -MaxMessageSize 20Mb

Per-user settings should only be used as exceptions to org settings – they’re not set by default. Use this command to get a list of all mailboxes with MaxSendSize or MaxReceiveSize set to a non-default value:

Get-Mailbox -Filter {MaxSendSize -ne $null -OR MaxReceiveSize -ne $null} | ft Name,MaxSendSize,MaxReceiveSize

https://cinchit.com/how-to-set-exchange-2013-email-message-size-restriction/

Get-TransportConfig | ft MaxSendSize, MaxReceiveSize
Set-TransportConfig -MaxSendSize 50MB -MaxReceiveSize 100MB

Get-SendConnector | ft name, MaxMessageSize
Set-SendConnector <Connector Name> –MaxMessageSize 50MB

Get-ReceiveConnector | ft name, MaxMessageSize
Set-ReceiveConnector <Connector Name> –MaxMessageSize 50MB

Get-mailbox | ft Name, MaxSendSize, MaxReceiveSize
Set-Mailbox "User Name" –MaxSendSize 50MB –MaxReceiveSize 50MB

https://cinchit.com/how-to-set-exchange-2013-email-message-size-restriction/