Using HTTPS with OXtender for MS Outlook on Windows Vista doesn't work

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Concern:
You are trying to connect your Outlook-Client on Windows Vista using OXtender to an Open-Xchange Server via HTTPS encryption but connection to OX Server will not be established and synchronization of the groupware data between Client and Server fails. When omitting encryption and only using HTTP to synchronize groupware data everything works as expected.

Reason:
The usage of Outlook-Client on Windows Vista is linked to Internet Explorer 7. In order to use HTTPS to connect the Outlook-Client to the OX Server a Certificate is necessary which is issued and signed from the OX Server Certification Authority. For Internet Explorer 7 the OX Server Certification Authority is not a Trusted Root Certification Authority yet, hence any encrypted connection using the Certificate issued by OX Server Certification Authority will fail and will be rejected not only for browsing in IE7 but also for the Outlook-Client to connect to your OX Server.

See also:

http://msdn2.microsoft.com/en-us/library/bb250503(d=printer).aspx

[...]

As a user of Internet Explorer 7, you can work around the compatibility impact of HTTPS Security Improvements in the following ways:

If the certificate was not signed by a trusted certification authority, you can add the certification authority if you trust the authority.

Trusting a malicious certification authority will put your computer at risk, so use discretion. To add a Trusted certification authority, continue navigation from the Certificate Error page, and then click the Certificate Error button in the Internet Explorer address bar. Click the View Details link. On the Certification Path tab, select the root certificate and click the View Certificate button. On the General tab, click Install Certificate.

[...]

Solution:
In Windows Vista start IE7 and go to:http://IP-address-of-your-server/CA.crt

Execute the following steps:

  • in "File Download - Security Warning" - popup window

"Do you want to open or save this file?" click "Open"

  • in "Internet Explorer Security" - popup window

"A website wants to open web content using this program on your computer" click "Allow"

  • in "Certificate" - popup window

click "Install Certificate..."

  • in "Certificate Import Wizard" - popup window

click "Next"

  • select "Place all certificates in the following store"

click "Browse"

  • select "Trusted Root Certification Authorities"

click "Finish"

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