Hi Devendra,
Use the Domino admin to read the log file. Enter log file in your Notes help search. Go to the menu select help select search.
You will also find data in the miscellanious events - in the admin program (admin.exe).
I suspect your out of disk space on the Domino Drive. If so I would look at the file sizes of the users email files and run a compress with file reduction then restart the system. There is also a diskcashe cleanup agent on the server that should be running automatically.
If you have space and cashe.dsk is still your problem rename it to cache.bk
Domino will create a new cache.dsk when it starts. If this solves your problem. then delete the cache.bk as it is only a system work file. Many domino system files (not data) will be recreated if Domino cant find them. Under v 4.2 the smtp mail would get currupted copying the docs and deleting the file would fix the mail jams.
Good luck.