To avoid any disruptions of the services provided by Netmail, it is extremely important that Windows updates be handled as part of normal Change Management activities. They should therefore be planned, not simply applied as they become available. Moreover, any updates that affect the applications and components required for the operation of Netmail platform must be avoided. Such updates could "break" the Netmail applications.
This being said, minor Windows updates are generally safe. However, on occasion, they can cause services of the Netmail solution to hang and/or fail to restart correctly. Automatic application of updates, therefore, must be turned off. When updates are applied, all systems that may be potentially affected by the updates (including the Netmail platform) should be monitored for a time to ensure that they continue to be fully operational.
In the case of the Index Server, ensure that you pause the indexing and stop the services. It is a good idea to use a regularly scheduled index backup window, during which the indexing is paused anyway, to perform a Windows update. For more on the subject of backing up and restoring the index, please refer to the Backup and Restore section of the Indexing Best Practices page in the Netmail Archive Technical Notes.
Major updates, or OS upgrades (e.g., going from Windows 2008 to Windows 2012), must only be done once Messaging Architects has had time to validate that the Netmail platform is in no way negatively affected by changes made by Microsoft.
By verifying what exactly is affected, and doing a little bit of planning with respect to applying updates and upgrades, you can avoid negatively affecting users and keep the time required to maintain the solution to a minimum.