I got this last night from MailStreet:
Dear MailStreet Customer,
We wanted to update you on a problem we experienced that may have affected your ability to connect to your MailStreet Hosted Exchange service today between 4:30PM and 5:10PM Eastern. Although many customers did not notice an issue, we feel its best to be forthcoming in this matter.
The problem has been identified as a faulty core network switch in our datacenter. This equipment was replaced and the connectivity issues have since been corrected. Please note that the problem was network related and did not result in any data loss.
We apologize for the inconvenience this may have caused you and your organization. Please know that we are working with our datacenter vendor to find a way to prevent such an occurrence from happening in the future.
We thank you for your understanding as we worked to correct this issue. We appreciate having you as a MailStreet customer.
866.433.8787 x 2