Resolution:
You can use following steps to login to EMS Server as sAMAccountName in Microsoft Active Directory server:

1. Make sure your LDAP setting in EMS main configuration file uses CN as user attribute: ldap_user_attribute.

2. Modify your ldap_user_filter to check sAMAccountName, ex:
   ldap_user_filter               = (&(sAMAccountName=%s))

3. Disable your LDAP cache by commenting out:

       #ldap_cache_enabled       = TRUE
       #ldap_cache_ttl                 = 0

4. Then login EMS Server through EMS client using sAMAccountName as user name.

The following is a sample LDAP setting:
ldap_url                          = ldap://ldaphost:389
ldap_principal                 = "CN=user9 D,OU=production,OU=ACCOUNTS,DC=ems,DC=support,DC=com"
ldap_credential               = Tibco123
ldap_user_class             = person
ldap_user_attribute         = cn
ldap_user_base_dn        = "OU=ACCOUNTS,DC=ems,DC=support,DC=com"
ldap_user_scope            = subtree
ldap_user_filter               = (&(sAMAccountName=%s))

#ldap_cache_enabled     = TRUE
#ldap_cache_ttl               = 0