Outlook over HTTPS, now renamed to Outlook Anywhere, is a great feature that we use in-house and at a number of clients. It basically gives you Exchange connectivity outside of the network without using a VPN. I use it on my laptop as my primary profile and it means Outlook works whether I’m in the office or not.
After recently deploying SBS 2008 in the office we noticed Outlook would struggle to connect over HTTPS. Once connected it would generally work without a problem for a number of hours, but it would then become un-responsive and we had to move to OWA while it recovered. If you left Outlook it would generally recover, although it could take up to an hour.
I raised this with my ever resourceful friends over at microsoft.private.sbsc.windowsserver.sbs and yet again they came back with the right answer. In our case that was the TCP Chimney Offload problem, as described in this MS article.
Following the above article I found that TCP Chimney Offload was already disabled in the OS, but not on the network card. First of all I replaced the network card drivers that the SBS setup had installed with the correct drivers from HP. Then in the Advanced tap of the network card properties I set ‘Receive Side Scaling’ to disabled.
These two actions together have cured all the problems we were having with Outlook and another hats off to Robert in the newsgroups.
