I asked, "What did you see in the Send/Receive group when you looked?"
While viewing the Inbox, press ALT-CTRL-S. How many send/receive groups
do you see? Select each Send/Receive group and click Edit. How many
accounts and which ones do you see there?

I see two groups (That is, I see "All groups" plus group X plus group Y.)

I hardly dare to tell you, but I suddenly realise that I don't see the
"duplication" anymore. I did not change anything in the settings. Come to
think of it, perhaps it's only now and then that the phenomenon occurs. A
few years ago I had the same thing on my previous computer but then it was
like a fourfold version. The reason I am asking now is that I think I may be
doing silly that causes this problem.


I'll ask another as well: what is your send/receive interval value?

Do you mean the interval between automatic checkings?
5 minutes.

Thanks for your patience.