>> However we encounter some problems with the NameID format. The Service provider expects a NameID=emailaddress@gmail.com but Gluu sends instead of the email adres a strange value "_7301855dbf4bf5a9520629e8d456e796" to the service provider.
John,
'transientID' is the default NameID which you can use from IDP. For our customers Gluu Engineers build new custom NameID ( i.e. which can grab and send values as email_address you need ).