Hello Everyone, My company recently migrated our Exchange server from 2003 to 2010. After the migration, we noticed that the exchange server automatically changes Outlook Client settings from basic connection to "Connect to Microsoft Exchange using HTTP". It's somewhat random. It doesn't happen all the time, but recently it's starting to happen alot. It hit one of our company owners client and he's quite upset. Anyone have an idea on how to turn this off or set to not automatically change our settings? Thanks, Aaron Haughton

Outlook will connect using HTTPS instead of TCP when they can't connect using TCP. You should look into the network configuration, firewalls in the path, or the existence of multiple networks.Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

So, you're trying to say it's a firewall issue. What ports or applications do I have to unblock to send emails to the exchange server? Another part of this puzzle is this: The users are saying that they're only having this issue when they send attachments in their emails. Without an attachment it's ok.

What I'm saying is that Outlook doesn't think it's able to connect via TCP so it's trying to connect using HTTPS. You can try fidgeting with the settings in Outlook to see if you can force it to use TCP, but I suspect that you have something going on with your network that's fooling Outlook.Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

You do not mention which version of Outlook is in use by the clients. Outlook 2007 and newer will use Autodiscover to find the connection information to the mailbox. If Outlook Anywhere is enabled on the client access server, then Autodiscover will set the Outlook Anywhere connections in the client profile automatically. The only way to disable this function of Autodiscover is to disable Outlook Anywhere on the CAS. In the Outlook profile, there are two settings that affect how Outlook tries to connect with MAPI or HTTPS. Open the Outlook profile and go to the server settings page. Then go to more settings/connection/Exchange proxy settings. How are the options for "On fast networks, connect using HTTP first, then connect using TCP/IP" and "On slow networks, connect using HTTP first, then connect using TCP/IP" set? Based on the behavior you describe, I suspect that Outlook is connecting with TCP/IP first. Then at some point losing its TCP/IP connection with the server. Outlook then thinks it is on a slow network and connects with a HTTPS connection. Looking at the network layer is a good first step. I would start with network drivers and settings on the Exchange server and workstations. This article explains more detail around Outlook 2003 when this issue occurs for this client. http://support.microsoft.com/kb/910346#top The behavior will be similar for Outlook 2007/2010 clients that loose the TCP/IP connection as well.