NT Backup of Exchange 5.5

Good day,peers.I am studying backup routines in NT 4.0.I am aware of NT not backing open databases in Exchange ,priv.edb,pub.edb although the literature i am reading states ntbackup can be used for online backups i have noticed skipped files in my log.I have scripted my backup to run @ specified schedule both normal & diff.I was reading a
question on this site about stopping my service in my script & running the backup which I tried to emulate but ALTHOUGH IT IS A VERY ELEMANTARY QUESTION I donot know which command for exchange to stop.net help services does not inform me of messaging services.I have tries net stop IS,DS,but no success.Any help would be appreciated.With Veritas Exec 8.6 backup is relatively efficient.Thanx