Thanks David,
Permissions were already checked, thanks.
Issue solved.
Im ashamed though. Problem was all files were missing the final dot. Info
was recovered from the server's dead HD
with a windows application, then copied back to the new Linux server running
cyrus. Thus, files dots were ripped
Update from my first post:
Created a new folder from thunderbird, copied some messages from another
folder into it and no problem, I can see those messages (all this from
thunderbird)
I can see those messages on the server too of course. Now, I copy files from
another folder into that new folder