How do I convince apple mail to use the SAME "from" address as addressed to when replying?

I received an email at address A. All is well and fine until I reply, Apple Mail (Sierra) decides to use a different email address (the top one in the Accounts list?). To repeat, if I get an email addressed to address A and I reply to it, Apple Mail substitutes email B, which is getting old really quickly. This is a new behavior since the last update of Sierra (I cannot update to High Sierra because of some older software still in use).

I have seen in older advice that the list used to be able to be rearranged but that does not appear to be easily done any longer.

I have also seen in older advice that if I change the outgoing serger for the top account that Apple Mail will automatically switch to the chosen outgoing from address - That does not work either.