Exchange Development Kit (EDK) connector 'Text Messaging Delivery Agent Connector' was found in the organization. Exchange Server 2010 does not support EDK connectors. This connector will need to remain on existing Exchange 2003 servers.

When running Microsoft Exchange Pre-Deployment Analyzer before installing Exchange 2010 into environment with Exchange 2007 installed, an informational error is shown saying that some legacy connector, you probably never heard of, exists. In my case the environment was Exchange 2007 and the connector was found in Exchange Administrative group (FYDIBOHF23SPDLT) using following steps:

1. Connect to your DC
2. In the Active Directory Sites and Services Microsoft Management Console (MMC), double-click Active Directory Sites and Services.
3. Click on top level in the hierarchy tree aka Active Directory Sites and Services (yourdc.yourdomain.com)
4. On the View menu, click Show Services Node.
5. Double-click Services, double-click Microsoft Exchange, and then double-click the Exchange Organization name.
6. Double-click Administrative Groups, and then double-click the administrative group - OLD one (Exchange 5.5 or 2003) OR Exchange Administrative group (FYDIBOHF23SPDLT) – This connector can be found in different groups according to the information on the Internet.
7. Double-click Routing Groups, and then double-click the routing group. For example, double-click Exchange Routing Group (DWBGZMFD01QNBJR).
8. Double-click Connections.
   On the right side of the MMC, you can see the Text Messaging Delivery Agent Connector.
9. Delete the unnecessary connector