Essentially, NHServer is the program that processes all items in and out of the database, such as emails, calendar appointments and so on.
The program is run interactively (opened, and “Start Repeated Scan” clicked), where it will continue to poll, as long as there is a logged in session.
However, some prefer not to do this, in case the server session is ever logged off. To get around this, it is possible to set up a scheduled task, which will open the program for you, run a single scan, and close itself down. It will do this on a schedule, usually set to run every 5 minutes. This means a logged in session is not needed for the email process to run.
If you have experienced issues with NHServer, the Support team may advise you to run interactively rather than scheduled, it is usually temporary, whilst a fix is being identified. It is usually due to something stopping the NHServer process from running, so the task never completes. NHServer essentially gets stuck.
To setup a scheduled task, if NHServer process ok, on the machine NHD is installed on (usually a server), open up Task Scheduler, a Microsoft product available on most Windows platforms.
The fundamental points for setup are as follows. Values are examples: