Dear Cheryl, good day,
Once more my thanks for your response.
Because I'm rather conservative with upgrading
my upgrade to Sierra, came from Mountain Lion (10.8.5).
My present problems confirm to me that I should be even more patient in the future.
Yes, I have quit Mail and relaunched it.
No, it did not solve the problem.
Yes, I have quit all apps and yes, I restarted the computer and yes, I gave Mail a new try.
No, it did not solve the problem.
Yes, the Combo update 10.12.4 was downloaded and installed (after upgrading to Sierra).
No, it did not solve the problem.
Conclusion?
No, the issue has not (yet) been corrected.
Please allow me the following question:
On your (Mac I assume) computer,
can you drag an eMail from your eMail inbox
and drop this same eMail in the sub-directory of an other Mailbox
in one smooth and uninterrupted action, without any additional clicks?
Do you perhaps know if Apple is even aware of this problem,
let alone interested/committed to solve this problem?
On a more philosophical note;
whereas on the one hand I agree
that developing new software for Apple's first selfdriving car
is far more sexier than solving an old eMail drag & drop problem,
Apple should never forget, that buyers of the old, make possible the new.
One of these days I might send you a (polaroid) image
of my six years old daughter playing with my Apple ||e
(complete with 80 characters display and IBM 8" floppy drive).
Regards
Eurob