I have many complaints from customers i support that when rebooting SBS 2003 servers the users get loads of NDR's from emails months before. not only that people will call asking why they are re-sending emails.
I have checked the queues before a reboot and dont see anything there.
All mail is being sent via a smarthost of the ISP. i can confirm mail transport is fine under normal daily working.
Hardware varies with Dell, HP and FS. Software is all Windows 2003 SBS R2 SP2 with exchange 2003 SP2. all customers also run Trend SMB V3.x and one customers runs GFI mail essentials latest build.