@girish Wouldn't it make sense to create hardlinks instead of symlinks for these folders so that you don't have duplicate folders? Ar am I overlooking something?
The cloudron backup logic does not understand hardlinks. It would then end up taking backup of your junk folder twice. This is unlike symlinks which is ignored by the backup code. Neither the symlink nor the contents of a symlink are backed up.
This does bring up an important point that if you move your mail server to a different server, you have to remember to create this symlink by hand again!