Open Exchange Management Shell
Type in get-receiveconnector
This will list all of your receive connectors
Next type in
set-receiveconnector -identity ServerNameInternet -ConnectionTimeout 00:30:00
This command will change the timeout to 30 minutes.
Use this command to get all your receive connectors and change them all to 30 minutes
get-receiveconnector | set-receiveconnector -ConnectionTimeout 00:30:00