I have installed Exchange 2013 in Exchange 2010 environment everything working fine except outlook autodiscovery for exchange 2013 users. If I change EXPR frommsstd:e2k10ht.abc.com tomsstd:e2013ht.abc.com Exchange 2013 outlook Auto discover working and Exchange 2010 user outlook prompt for password .
[PS] C:\Windows\system32>Get-OutlookProvider
Name Server CertPrincipalName TTL
---- ------ ----------------- ---
EXCH msstd:e2013ht.abc.com 1
EXPR msstd:e2k10ht.abc.com... 1
WEB 1
Regards
Bhupen