To resolve it, we need disable the HTTP redirect setting. On FE ex2003 server, open IIS manager, expand “Default Web Site”. In the right panel, right click “HTTP Redirect”. Clear “Redirect requests to this destination” option to disable the HTTP Redirect
setting. Click “Apply” to save the change.
Then, open IE, typing your URL https://webmail.domain.com/exchange, input Exchange 2003 user’s user name and passwords, check whether Exchange 2003 user could log into OWA, check whether the problem is resolved.
Check the Default Web Site and see if we have SSL checked.
If so uncheck the SSL on Default Web Site and then it should redirect /exchange from http to https
Make sure Exchange 2003 FE has enabled form based authentication (FBA) checked
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Note: This settings is for Exchange 2003 server only.