Each folder window has the same column bars: from, subject, date/time, size.
Also the assigned "Copy to Self" folder has these predefined columns, but when a sent mail is being copied into it, the "from" column contains entries like: "To: addressee". This might be accepted when working only with Pmail.
But when using different mail clients (e.g. Thunderbird) to access one mailbox, these other clients always enter the real sender address, means my own address, into this column. And that is correct behaviour since the column is named "From".
"Copy to self" folders should get a real column "To" instead of abused column "From".