Hi Vila,
I want to bring in this again, that this happens once in a while and when it happens it basically starts failing the messages. This is an intermittent behaviour, and it resolves it by itself.
Down point is, we have to process the synchronous messages manually during this period which is a lot of work to do again. We want to troubleshoot why this happens intermittently and ever since past few months this is more frequent.
I checked the note you mentioned about and all the Exchange Profile parameters seems to be correct as the messages are processed until we again see this error. So username/password and all these parameters are correct else it would not work at all !?!