There are 3 different reasons listed under Notes on the mass email delivery report.  They are "Held", Opted Out" and Duplicate.  It is important to be able to distinguish the accounts in each of these three buckets so that they can be handled perhaps differently depending upon what the reason is.   Showing these noted in a custom query would work since then it can be exported and the accounts in question can be selected, edited and uploaded.  For example, if we had a listing of the accounts with the "Held" status, we can mark those emails as invalid in eTap (in a UDF).  Whereas we may not want to do that for the other 2 categories.