Microsoft has confirmed that this month's Windows Server security updates are causing problems for some Exchange Server deployments. The updates are interfering with Outlook Web App (OWA) sign-in and mail delivery, according to the company.
On affected systems, users may be unable to log in to OWA, and mail flow can be disrupted. Microsoft has not yet provided a workaround or fix, and the company is investigating the cause of the issues.
Administrators who have applied the October updates should monitor their Exchange environments for these symptoms and watch for further guidance from Microsoft.