While attempting to migrate to Exchange 2013 we ran into a problem.  We mostly have Outlook 2007 clients with a handful of Outlook 2010 clients.  All the mailboxes that have been migrated to the 2013 server and have Outlook 2007 are getting the  "Outlook is unable to connect to the proxy server. (Error Code 10)" and login prompt.  All of the mailboxes on 2013 with Outlook 2010 work without any issues.  All connections from the outside (OWA and Outlook Anywhere) work without issues.  The only problem is with Outlook 2007 on our internal network.  We have a multi-domain certificate pointing to the outside for OWA and Autodiscover.  We have split DNS set up with OWA pointing to the inside 2013 server ip address.  Outlook 2007 and 2010 are getting the same correct information from autodiscover.  I have tried creating a new Outlook profile without any luck.

Is this Microsoft's way of killing Office 2007?

Any suggestions??

• Edited by j_p_76 10 hours 42 minutes ago

Hi,

Please run the below command:

Get-OutlookProvider

For Autodiscover service, please run Test E-mail AutoConfiguration to check if the connection is successful in Log tab and confirm the other services URL can use proper namespace in Results tab for request access.

If the Autodiscover service fails, please create a SRV record with mail.domain.com for Autodiscover service to have a try.

In addiction, I have found a similar thread for your reference:

https://social.technet.microsoft.com/Forums/office/en-US/a8e6a8d6-8600-42e7-bdfc-8aaa8ad8b467/outlook-is-unable-to-connect-to-the-proxy-server-error-code-10?forum=exchangesvrclients

Regards,

David