I am not able to put proper title for this question, but i will try to explain it here.
If I know that there are many files in this directory:
https://mail.google.com/mail/e/
like
https://mail.google.com/mail/e/320
https://mail.google.com/mail/e/ezweb_ne_jp.059
...
and many more.
But I can not list them, since directory listing might be denied as in above case.
Is there any way to list all such files. Or any workaround?
No, it is not possible. As far as I know you cannot get the list of all files or directories without the directory listing enabled. This cannot be done directly or there is no easy way to do this.
If you really want to find out the list of files, you will have to crawl the site and find all the links that are pointed to that directory. However, this method is not guaranteed to give you list of all files and directories as there may be many files which are not linked from anywhere and are just present there, some files which might be accessed in only some specific cases, etc. Also, if the sites see lot of traffic from your user or IP they might just ban your from the website.