How to use Telnet in Exchange Server 2010

Telnet utility is used to test SMTP communication between messaging servers and has been used by the administrators from a long way back. To use telnet in Exchange Server 2010, below requirements should be met:-

· Receive Connectors should be configured to use Anonymous or Basic authentication for internal Hub Transport servers, and only Anonymous access for internet-facing servers.

· Install Telnet client utility on Windows Server 2008

By default, SMTP listens on port 25.

Let's analyze the responses received when you use Telnet on SMTP.

1. open mail.techpeoples.net 25

2. EHLO fabricam.com

3. MAIL FROM: mike@fabricam.com

4. RCPT TO: sachinm@techpeoples.net

Open mail.techpeoples.net 25

The cause of failure in connection may be source/destination firewall, Incorrect SMTP address/port, or destination SMTP service is unavailable.

EHLO fabricam.com

A failed response will display error as Invalid domain name and the possible cause may be invalid domain name characters or connection restrictions on the destination SMTP server.

MAIL FROM: mike@fabricam.com

A failed response error will be either Invalid address or Client was not authenticated and the cause of this response may be that the destination server does not accept anonymous connections.

RCPT TO: sachinm@techpeoples.net

The failure response would be User unknown and possible reason of the failure would be non-existence of specified recipient in the organization.