When connecting a Windows Mobile 5.0 device to the Exchange Server, a certificate error message appears:
“The security certificate on the server is invalid. Contact your Exchange Server administrator or ISP to install a valid certificate on the server”. Support code: 0x80072F0D
However, there is a valid certificate installed. It is signed by "Go Daddy Class 2 Certification Authority". Outlook and Outlook Web Access work with Exchange Server without any issues.
The problem appears only when connecting to Exchange Server via Active Sync using your Windows Mobile 5.0 device without the AKU2 (Adaptation Kit Update).
If you use your Windows Mobile 5.0 device without the AKU2 installed, GoDaddy’s root certificate and all child certificates are marked as not trusted. As a result, your Windows Mobile 5.0 device claims an invalid SSL certificate and will not connect to the Exchange Server.
Install GoDaddy's root certificate to your Windows Mobile 5 device using instructions from GoDaddy. Link to https://certs.godaddy.com/InstallationInstructions_alt.go
Please find an alternative resolution below:
1. Open the link to Outlook Web Access in Internet Explorer on your Windows Mobile 5.0 device, https://exchange.domain.com/owa. See screen shot below: