Thankyou Sparkleberrry, Although it doesn't solve the problem, at least you have explained why it happens, and a solution is up to Apple. I am certainly not going to move names around within the body of the mail, every time I want to send a message to the group.
I have one group of 25, and if you want to be sure (at a glance) that everyone is included, that is what computers are for……..
The names start within Address Book in alphabetical oder, why should the unique ID be different ? You are correct to say that I should suggest to Apple that the present system is "Untidy, confusing and within their knowhow to fix" (we need an astuce, which once the names are in the address list in the customary jumbled fashion, one has to ^shift click Bingo^ and the list becomes alphabetic.)
Have a nice evening 21:45 here, and thankyou
Eric
p.s. In addition to your reply, I received 6 others , subject listed in each case as (iCloud on my Mac) which had absolutely nothing to do with the subject. This is very un-Apple.
again thankyou, Eric