After a self signed certificate that exchange creates when Exchange Server is installed has expired, you’ll have to renew the certificate on the Hub Transport and on the Edge Server if there is one.

You know you’ll have to do this if you find the following error in the eventlog of the Exchange Server.

Log Name: Application
Source: MSExchangeTransport
Date: 24.08.2010 10:48:21
Event ID: 12019
Task Category: TransportService
Level: Error
Keywords: Classic
User: N/A
Computer: server.domain.local
Description:
The remote internal transport certificate expired. Certificate subject: CN=edge.

To view the currently installed certificate use the Get-ExchangeCertificate ¦ List cmdlet
To create a new certificate you should use the New-ExchangeCertificate cmdlet.

You’ll have to create a new certificate on the Hub Transport as well as on the Edge server. You’ll have to re rebuild the EdgeSubscription on the Hub Transport server.

You can follow the instructions on the following page. Here
The Microsoft Event Description can be found on the following page. Here