Message send and receive limits are by default set to 10MB. This is usually a problem for a lot of users due to the need for sending large attachments or multiple attachments. Since Exchange 2010 was launched the demand for sending large attachments has increased dramatically, most email provides support much larger receive sizes e.g Google support 25MB attachments.
Anyway, to increase the limits in Exchange you can do either of the following;
The first way is to use the Exchange Powershell;
Run these commands below, the change needs to be made in multiple locations so there are multiple commands.
Set-TransportConfig -MaxSendSize 25MB -MaxReceiveSize 25MB
Set-ReceiveConnector “your-connector-name” -MaxMessageSize 25Mb
Set-SendConnector “your-connector-name” -MaxMessageSize 25Mb
Once you have made those changes you can also set a particular mailbox to have a lower Send/Receive limit using this command;
Set-Mailbox “John Smith” -MaxReceiveSize 15Mb -MaxSendSize 15Mb
The second way is to use the Exchange Management Console (EMC);
Firstly we are going to edit the Transport Settings
Browse to Organization Configuration > Hub Transport > Global Settings > Transport Settings, click properties and you’ll the see the screen below. Change the values accordingly
Secondly we are going to change the receive connector
Browse to Server Configuration > Hub Transport > Receive Connectors >Select the Connector > Properties…Then set the required values
Finally we are going to set the Send Connector limit. Before you increase this I would suggest checking with your Smart Host or Relay the maximum sending limit you can send through them otherwise you’ll find another barrier to over come. Usually with the smart hosting I’ve dealt with I’ve found it to be 50MB. If you send through DNS then you don’t have anything to worry about.
Browse to Organization Configuration > Hub Transport > Send Connectors, select the send connector > Properties…Then change the values accordingly
Send a test message and see if that’s working now. I’ve seen in the past that it takes up to 24 hours for the Outlook clients to accept the new send limit.