[Dovecot] Filenames and flags

Hi,

Does anyone know how the filnames as created and/or if you can read a mail's flag or status from it?

1 .As you can set i.e. "ToDo" label on a message and then if I open from another thunderbird I can see it is marked there aswell I wonder: Is this read from the filename or some registry?

2 .Can I understand from a filename if a message is read?

3. Sometimes when I try to filter with flags no messages show. Is this a thunderbird bug or a dovecot one, or one in conjunction?

Best regards -Jon