Open Exchange Management Shell and start by checking your Send Connector(s) :
Get-SendConnector
You should get the name of your send connector(s) – like “Default Send Connector”.
If you haven’t messed up with the port configuration of the connector yet,
it should be using the default port -25. It is a good idea to confirm this with the command:
Get-SendConnector | fl port
Read more: Smart Host using Port 587
