Symptoms
In Exchange MRSPROXY.SVC FAILED BECAUSE NO SERVICE WAS LISTENING ON THE SPECIFIED ENDPOINT. THE REMOTE SERVER RETURNED AN ERROR: (404) NOT FOUND
Exchange 2010 / 2013
You get an error when you’re trying to setup Hybrid configuration between your Exchange On-premises or Online.
After I had one issue like this I did some research and used Fiddler / Wireshark to check for traffic I noticed that the traffic on the server is not encrypted and testing the Migration Server Availability was reporting that the MRS service was not listening on the supposed port which is 443.
CAUSE
This problem may occur if the ExchangeGUID property of the Exchange Online MailUser object does not match the ExchangeGUID property of the on-premises mailbox. To successfully move a mailbox, the value of the ExchangeGUID property in the Exchange Online mailbox and in the associated on-premises remote mailbox must match.
In this case the solution was pretty easy, but still you’ll have to make a hard choice of choosing to place Exchange behind a load balancing with SSL Offloading on or not.
In my case I had to turn off the SSL Offloading on the Load balancer and that alone was enough to get this working.
Resolution:
Make sure that SSL Offloading is disabled on OWA/OA and Load balancer if there’s one.
Other resolutions:
https://support.microsoft.com/en-us/kb/3065754