I recently did a sbs2003 to sbs2011 migration that went well but had the default remote.domain.com settings in the self cert owa etc. I changed that to reflect the external DNS setup and installed a bout SANS UCC cert which works a treat apart from once a day I get a SSL cert error on the outlook 2010 clients at around luch time, Ive been through all of the settings on the GUI and also changed the ones from the command line. Initially I was getting 2 of these as you opened outlook and these are now sorted but this last one that pops up at lunchtime is eluding me. Any ideas where it might be coming from??