1) can you run the following command for organization level operations;
Set-TransportConfig -MaxReceiveSize 32MB -MaxSendSize 32MB
or Organization Configuration | Hub Transport | Global Settings tab | Transport Settings | Go to properties and set values from there.
2) For Recieve Connector settings ;
Server Configuration | Hub Transport | select a HT server | Receive Connectors -> select a connector | Properties | Define Maximum Message Size from General tab.
or run this command : Set-ReceiveConnector “CONNECTOR NAME” -MaxMessageSize 32Mb
3) For Send Connector values ;
Organization Configuration | Hub Transport | Send Connectors -> select connector | Properties | Switch to the General tab and define the Maximum Message Limit value.
Or run the command: Set-SendConnector “CONNECTOR NAME” -MaxMessageSize 32Mb
4) For Mailbox limit definition ;
Recipients | Mailbox -> select mailbox | properties | Mail Flow Settings tab | You can define values in Message Size Restrictions .
Or run the command : Set-Mailbox “Joe Adams” -MaxSendSize 32Mb -MaxReceiveSize 32Mb
perform the above operations. then restart the information store and Mail Submission services.