All Exchange admins are familiar with the SMTP banner. It is the response received by a remote server after it connects to the receive connector of an Exchange 2010 Hub or Edge server. If the SMTP banner is not set on a receive connector, the default response will have the fqdn of the server, along with the information that the server in use is a Microsoft one.
Below is the default response from my telnet client. As the internal information becomes visible to outside servers, exchange admins tend to change it.
I have seen companies using the “Specify the fqdn this connector will provide in response to EHLO” option in the receive connector as a means to set the banner. It is NOT the right way to do it.
The “banner” parameter of the Set-ReceiveConnector cmdlet needs to be used to configure the banner. Run the command below to set the banner. The banner text should start with 220, as stated in RFC 2821.
Set-ReceiveConnector –identity “ServerConnectorname” –Banner “220 banner text”
Once it is set, a telnet session will respond with the new banner.