Конфигурация MS Exchange 2010 SP2, Windows 2008 R2 SP1.
В EventLog посыпались:
Очень хорошиий ответ: ТУТ
Some IT guys recommend to disable SCHannel logging to get rid of these events, but I cannot recommend that. To be honest. It is better to see, that somebody is trying to connect using HTTP on HTTPS port, because this might be some attempt to DoS attack or info, that users don´t know how to type OWA URL correctly. Shortly it is better to know something is wrong than disable logging.
I suspect wrong redirect configuration for the websites from HTTP to HTTPS. I would check IIS if redirect is set correctly. For those having this issue without redirect I would suspect problem in web browser area.
Сделал перенапраправление HTTP: