While Upgrading SMG which is on 10.0.2 > 10.0.3 > 10.0.5 . with a Contorl Center and two scanners, all of them are running on a seperate appliance.
When a scanner is being upgrade then you have to stop the mail flow to that scanner. While this is happening are mails not being accepted or delievered ?
How the scanners are updated by making sure that mails are not rejected.