I found that with mailx, I could either make an attachment OR pass a message. But, I could not do both. Because of the nature of my specifics, I often had more than one attachment. Thus, I created a loop to send all my attachment messages one-at-a-time, and then send a summary email.
I have been told that there are other mail utilities available for unix that can accomodate the attachment and message. Perhaps someone here can add the name(s) of other utilities. [Or, let us know how to get the syntax to work.]