Why lftp mirror --only-newer does not transfer "only newer" file?

Question

I want to automate to upload files of my websites. But, remote server does not support ssh, so I try lftp command below instead of rsync.

lftp -c "set ftp:use-mdtm no && set ftp:timezone -9 && open -u user,password ftp.example.com && mirror -Ren local_directory remote_directory"

If local files are not changed, no files are uploded by this command. But, I change a file and run the command, all files are uploaded.

I know lftp/ftp's MDTM problem. So, I tried "set ftp:use-mdtm no && set ftp:timezone -9", but all files are uploaded though I changed only one file.

Is anyone know why lftp mirror --only-newer does not transfer "only newer" file?

Answer 1

mirror -R -n works for me as a very simple backup of new files