Exchange 2010 setup process fails if you try to install Exchange Server 2010 into a domain that has an underscore character ( _ ) in the domain name

If you try to install Exchange Server 2010 in a domain that has an underscore character ( _ ) in the domain name, the installation may fail on a pre-request rule. However, in this scenario, the Exchange Server 2003 installation can be successful.

This failure occurs because the Exchange 2010 Setup program creates a self-signed x.509 certificate for the server whose FQDN includes an underscore character ( _ ). However, X.509 rules indicate that the underscore character ( _ ) is not valid in X.509 certificate. The setup failure occurs in the Tlscertificateinfo.cs file, which throws the following argument exception: This failure occurs because the installation program does not find any valid DNS names in the Subject Alternative Name field of the self-signed x.509 certificate.

This behavior is by design.

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