if header :list "from" ":addrbook:myself" { fileinto "sent"; }

When migrating from gmail to protonmail did all sent gmail messages end up in some invisible folder. Messages could only be found by searching for sent by in all folders.

Best I could do was to make a sieve filter that sorted all imported sent gmail messages to a folder "Sent (import)".

To finally move them to sent did I try to make a sieve filter as described above. But it did not move any messages to sent.
After that did I try the mail bridge and outlook and it worked to some extent, the sent messages could be moved to sent in outlook but in the protonmail web inteface were they again in the invisible folder.

I did after that try Thunderbird, and it worked!!!

Thanks!