I just updated my version of Mountain Lion and then when I try to open my Mail app I receive this message :
I tried to reinstall Mail but I don't know how to do it.
Anyone know what the problem is?
The correct version of Mail.app for OS X 10.8.2 (in my case build 12C60) would be 6.2, so your version is too old. Try software update, if that doesn't show anything reinstall the OS X 10.8.2 Combo Update manually. Run software update again after (re)installing this.