This SMTP address being used, that is receiving the disconnection status, is this an email alias of the excahnge server primary email address?

The reason i am asking this, if you are using any address associated with your exchange account, than you will need to authenticate to that SMTP server to send email.

I also have an exchange service and several POP accounts, not associated with my exchange service, and 2 POP SMTP only alias accounts. These alias are associated to my exchange account and require me to be connected to authenticate before any email is sent out using the SMTP servers.

Keep me posted.