[Users] Duplicate incoming message into two different folders

[anton92 at gmx.ru]

On Tue, 16 Jun 2015 11:08:34 +0100
Paul <claws at thewildbeast.co.uk> wrote:

> This can only happen with filtering or processing rules. (Unless you
> also have another programme that is depositing msgs in your folders.)

I assure you that this is happening, and there is no filtering or
processing at all. I double checked.

I have been busy troubleshooting, so here are some more details:

the problem does not affect all accounts, but only two outlook.com
account (a third outlook account is not affected).

Now, whenever an email is retrieved from one of these two accounts, a
copy of it also gets stored in the other account.

I have checked that on the server there are no forwarding rules,
so I am sure that this is only a local problem that happens within CM.

While troubleshooting, I disabled one of these two outlook.com accounts,
then I sent to it an email. Result: the other account receives a copy
of this email, which is not addressed to it, as if it was the recipient. 
Then I did vice versa, and the same happened with the other account.

In short, whenever an email is retrieved from one of these two accounts,
CM places a copy of it into the other account too.
Then why does this not happen with the third outlook account?!? I don't
know.

For the sake of completeness, I have double checked that all the data
passed to the POP3 server from each account are correct and not mixed
up. I verified that each account has its own separate username.

Next I even checked that these data are properly saved in the account
settings plaintext file accountrc. They are, and each account has its
own separate data.

I really don't know what I could check now.

Could you please look into this?