1. Use reliable, properly sized hardware - All drives need to be redundant, don't use non-RAID disks. Make sure to have enough memory and processor available to handle your traffic.
2. Backup, Backup, Backup - Complete a full online backup as often as possible, if you have room in your backup window - backup nightly. Check your backups frequently (at LEAST once a month) to make sure they can be restored properly.
3. Use separate volumes - Use separate volumes for the OS, Exchange binaries and SMTP queue, transaction logs and database. Yes this sounds like a lot but this will ease recovery and improve performance. Even if some of the volumes are on the same physical RAID disks, Windows will have more threads to access the disk and thus can improve performance.
4. Run virus protection and attachment blocking - Virus protection is no longer a nice to have, it is essential. Update your virus definitions daily or hourly! To reduce the probability of being infected with viruses that don't have a definition yet, block common files types with your anti-virus product. Commonly blocked extensions (and file types that correspond), there are more please feel free to recommend additional: .BAT .CHM .CMD .COM .EML .EXE .JS .OVL .PIF .REG .SCR .SHS .VB .VBS .WS .WSH
5. Change Control/Do***ent everything - do***ent your Server configuration (including hotfixes installed), Exchange organization, connectors, mailbox layout, yes everything. Doing this will help you to be diligent about your change control, making sure to carefully plan and implement changes.
- Joel