Send connector %1 requires Transport Layer Security (TLS) before the MailFrom command but the server cannot achieve it. Check this connector’s authentication setting and the EHLO response from the remote server %2.

This Error event indicates the specified Send connector must use Transport Layer Security (TLS) for all messages that are sent to the remote server. However, the remote server is not configured to accept TLS.

A Send connector requires TLS for all sent messages when the RequireTLS parameter on the Set-SendConnector cmdlet in the Exchange Management Shell is set to the value $true. The default value is $false.

If the remote server is configured to accept TLS, the remote server displays 250-STARTTLS in the response to the EHLO command. If the remote server does not display 250-STARTTLS in the response to the EHLO command, the remote server is not configured to accept TLS.

To resolve this error, do one or more of the following:

• Configure the remote server to accept TLS. If the remote server is a Microsoft Exchange Server 2007 Hub Transport server or Edge Transport server, the AuthMechanism parameter of the relevant Receive connector must contain the value TLS.

  You can verify that the remote server accepts TLS by using Telnet on port 25 to connect to the remote server, and observing 250-STARTTLS in the response to the EHLO command.

• Configure the specified Send connector not to require TLS by setting the RequireTLS parameter on the Set-SendConnector cmdlet in the Exchange Management Shell to the value $false.

For more information, see the following topics:

• Exchange 2007 Transport Permissions Model

• Creating a Certificate or Certificate Request for TLS

• How to Use Telnet to Test SMTP Communication

• Set-SendConnector

• Set-ReceiveConnector

If you are not already doing so, consider running the tools that Microsoft Exchange offers to help administrators analyze and troubleshoot their Exchange environment. These tools can help you make sure that your configuration is in line with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. Go to the Toolbox node of the Exchange Management Console to run these tools now. For more information about these tools, see Toolbox in the Exchange Server 2007 Help.