Thanks for helping me with the POP or IMAP choice. I'm still not sure that I will move to IMAP after so many years of using my POP account. I'm not a fan of web based mail to begin with. As for alternate mail programs, only at gunpoint would I choose to use one. I'm used to Apple Mail, happy with it, not counting the current issues, and I don't want to learn a new program unless there's no other choice.
As for moving posts, I've lost track of posts too many times when dragging, and accidentally let go of the click. So I use the hierarchal menu Message/Move To option, and that serves me well. I do move posts between mailboxes (folders), but have not found a need to copy.them.
I used to run both TM and a SuperDuper or CCC clone, but, I've not replaced the HD for TM since it went soiuth. That was a couple of years ago, and I really haven't missed TM. I noticed that the upgrade to El Cap broke my CCC clone setup, so that I'll have to go in and take a look at it, maybe reset it. But, as things are, my clone is still running Yosemite, so I'm in no hurry to upgrade it just yet. I like to use WD Red HDs for clones, but, after getting used to my Fusion model on my internal HD, I get impatient with the old standard drives, even though I use only 7200 rpm drives. Maybe I should look at SSDs, but they're still pricey in comparison, and the Fusion drives are an good alternative. I'll probably grab another WD Red HD for the other external enclosure and start TM back up one of these days.