InC R&S IdP config breaks integration with R&S SP!

[David Bantz]

I recently switched our IdP configuration to support release to the InC SPs in the research-and-scholarship category.
Previously l had individual release policies for a subset of these SPs.  

The attribute filter policy provided at 
https://wiki.shibboleth.net/confluence/display/SHIB2/IdPAddAttributeFilterExamples or
https://spaces.internet2.edu/display/InCFederation/Essential+Attribute+Bundle+Config
releases the mail attribute

mail is allowed to be multi-valued, but releasing a multi-valued attribute for mail prevents login, 
with a message that the IdP is not releasing the required attributes.

I forgot that I had had to craft (resolve) a single-valued version of mail for FileSender and 
encode it with the mail OID.

I could release this single-valued version of mail for all research-and-scholarship SPs,
but am a little concerned this could create other issues down the road.

(FWIW, releasing both versions - that is two separate attribute clauses with mail attribute -
also blocks FileSender login, even if both clauses have the same single value.)

Your suggestions please!

David Bantz