One other note came via the ISO with respect to read receipts being a potential leakage of protected information:

We have consulted with the University System Information Security department.   If we were providing email for administrative use separately from students, it might be a different case, but when we include students the potential of private information leakage puts us in a different place. We just have no grounds to widely collect this information from students and it would be ultimately a liability  for us to have this information on file.   There is no granularity in this option for including only non-student IDs.