data Re-entry on refreshing prob??

I had made an internal mail service...Where user can send mail to other users...
Prob??
when user sends the mail .....and on refreshing , re-entry of data occurs........I want to remove this problem
Do anybody had idea about this..how to avoid the data re-entry from refreshing.....
Any suggestions and help are warmly welcome

assuming you're using a db to store the messages you could check for a duplicate entry before creating a new one.

Or you could redirect after doing the data entry part so the refresh basically doesn't do anything.
Or a combo, which is my preference. I use a timestamp and primary key combo to see if data should be entered as well as do a redirect after the entry. Covers both the refresh issue as well as user hitting "back" button.